I have tried mine with PC7 in the front and GQx in the rear they were ok but i did not like the feel of them. I settled on using the Rusty R2 Quad set and found them to great hold, drive, speed and pretty easy to turn under speed.
I haven't tried it as a Thruster yet but will hope to do so in the next few surfs, the Potatonator really lends itself to be ridden as a Quad as the tail is quite wide.
Don't think you can go too far wrong with the K2.1 quad set. I ran that in my Sweet Potato on Tuesday and had a blast. I'd probably run that in the Potatonator and throw in the Nubster when it was a little bigger or more punchy.