I have used the UL7 thruster set and I liked the flex in those they seemed to be more forgiving than the PG7 so I guess PC7s are somewhere in between. They seem like a good all round thruster set. I think they will go OK on the spit but I ride mine as a quad - it gives it a lower range. My spit is my grovel board.
The MF's are a very thin fin. Notiiceably thinner that the PC 7's. Intuitively you would think that a thinner fin means less drag and therefor it must be a faster fin but...thats not necessarily true. I own both sets of fins and have used both in various boards I own. For me the MF is a more flexy fin due to it being thinner and therefor I find the responsiveness to be a bit duller than the PC'7's. You do however get a touch more "twang" out of turns with the MF's compared to the PC 7's. I would be inclined to use the MF's on high performance boards and the PC 7's on board like the Spitfire which in reality you wont be surfing like a High Perf Shorboard. Hope that helps.
Gee I am really surprised at the feedback on the GMB's...I got a set about 6 months ago and absolutely love them...like really love them....I used them on my step up and they work a treat...horses for courses but I love that quad set up.
I've used them as a quad set in my JS Kinpin and they worked OK but just not in any of my Firewires. As a thruster set I think I tried them out on my Aloha AF2 and they went OK, but as you say different strokes.