At 155lbs the 5'10" will float you like a longboard. That board has tons of foam in it and a massive tail that,if oversized will cause trouble to move around.
My choice would be on the 5'0"-5'2" range for an intermediate surfer.
Now reading that you're experiencing problems paddling and despite the volume that this board offers, have you taken a look at the Addvance as well?Looks like you like boards with quite a bit of volume
If what's turning you down is the downsize, maybe it will be a good idea to look towards other models, like the Dominator which will add a few more inches into the mix.
What conditions will you be surfing the board mainly?.

I have a 6'6" swallow tail that has similar dimensions to the Addvance but isn't as wide and not as much volume in the front. It definitely doesn't have as much foam. My 6'6" works pretty well in more ideal waves and my 7" is kinda like my small wave board but I just dont like taking it out much. Generally it just doesn't feel really responsive and I can't pump the board much. It just doesn't feel lively. It's approaching spring so our swell will be dying down and the wave are generally in the 1-4ft range at best(I surf mostly beach breaks). And most of the time we dont have a whole lot of definition to our waves(in the spring/summer). I like the idea of the SP and part of it's appeal comes from it's volume. I was going with the SP because I thought I could get a lot of foam in a smaller more responsive board and could replace/contend with my 7" in terms of wave size for this coming spring and summer. Plus I thought it would be a good addition for those winter days when everything is blown out(which seems to be often =/ ). However if you think another model is going to be a better choice and a more versatile board I'm more then interested. I like the look of the patatonator as it has a different tail then my 6'6" and retains it's width more throughout the tail(something my current 6'6" doesn't do). Maybe in the 6'4" range?

I think the issue here is with oversizing, that's why you find your 7'0" is not responsive. At your weight seems like too much foam to be moved around. I think you should be downsizing a bit not only in length, but also in volume. For the kind of conditions you are describing, I would stick with either the Addvance or the Potato,both excellent stable boards
Do you have the chance over there to test the boards?? or at least see the boards mano a mano?

Unfortunately no. I wen't to my local retailer and they don't have any Potato's to demo, in fact they didn't even have a potato there. I didn't really look for the Addvance but I don't remember it being their. I know they had the Dominator though(although it isnt really in the discussion). Unfortunately none of my friends own a potato either so I'm a little in the dark. I feel like the Addvance is a very similar board to my 6'6" just with more foam and while I wish I could buy it too I feel like I should expand my quiver. . If I were to get a Potato how small should I go? Keeping in mind my skill level.

5'6" potato might be fun. i demoed a 5'8" because it was all there was available and it was huge for me. That said, I had a lot of fun on it racing down the line, but couldn't really turn it well because it was far too big for me. I'm going to be getting a 5'2" soon.

Considering your experience level and the frequency you surf I would go for the 5'4" max 5'6".The extra length/volume will help with the paddling issue

Thanks for the help. I'm still not 100% sure to be honest, I usually go out twice a week(atleast) but lately I havent been going more then once every 2 weeks and my surfing and paddling has suffered. I definitely realize that I need to go shorter then I anticipated with the SP.

Hey rocky, I agree with Iggy, don't even consider anything bigger than the 506. work as hard as you can to convince yourself that you are better off on the 504 and you will make it work and likely be happy you shave a little less volume...

cheers

Hey Iggy! i know this is an old subject, but i really need some advice from someone experienced like you to help me order the right size for me. I am 27 y/o 5'7, 170 lbs well built - been surfing for 15 years, ride 5'11 - 6'0 short boards with good experience and with an open mind. i tried the volume calculator on the FW website and it put me on a 4'10 SP, i am positively sure that i'm not going for the 4'10. I was thinking more towards the 5'2 or the 5'0 (minimum).. my question is will it make a big difference in performance if i'll choose the 5'2 as it is 4 inches bigger than what the calculator offered me or is there a thing with the calculator that just offers smaller boards than actually needed?, as if you can just fill in that you are intermediate and not inter/advanced and it will give you a completely different volume! my standard SB's are around the 26-27 vol. range -- Im just looking to ride it in 1-3 ft surf, and fear of getting a board that will be on the small side. I'll appreciate any kind of help, thanks in advance!

I'm 170lbs, standard shortboard volume 27-28l. I'm riding the 5'2 Potato. You could drop to the 5'0 pretty easy but the extra volume is nice for the smaller, weaker waves you'd predominantly surf the board in.
If you're in warm water the 5'0 could be a good pick.

Yup! Just came back from the FW retailer and ordered the 5'0 witch ill be surfing mostly in warm water (Israel), and can't wait to get it yeeewwwww!!! thanks alot prjwebb

you get to ride it yet raysal? interested in your feedback, I wanna get a small one too. I have been eyeing a 5'1 baked

Not yet, waiting for it to arrive hopefully in a couple weeks. Though i'm pretty sure the 5'0 will be perfect after more than a few people warned me not to oversize it and to get it as small as possible! Had a lil' chat with Nev Hyman and he also told me to get it even as short as u possibly think u can ride it, as long as it has more than a couple liters of volume over your other shorties you would be just fine! Ill let you know how it went after i get it and ride it nsjoel808!

yup im waiting for my boards too. Its a pain full wait, Iv never been frothing over getting boards so hard! lol
Thanks for reply & the info. The 5'1 felt like the one the first time i felt her up.