I originally built my full-sized guinea pig with gear as in the plans, minus the wheel pants. I had trouble with the plane wanting to tip over sideways and wing strike with that setup (the gear wasn't wide enough for the wingspan). I'm not entirely sure if that was because I added about an extra foot to the wingspan since I completely scratch built it, and the foam I used was longer than the dollar tree stuff. In any case, to solve, I used pretty thick wire to bend and solder wider gear, much like many old balsa planes used. I'll try to take a picture my final setup for you. With the wider gear (which also raised up the back end), I also was able to use a larger wheel in the front which also helped on the grass.