I like 1/6. Big enough to be a real project; not so big that it drags. Secret is the lighter the better. I have a VK Dr1 and it flies great; way better than I thought it would. I have The Camel in a box for a while, but I am doing a Reeves Camel. Hoping it will be a better contest plane. I built a Top Flite SE5a and it is a good flier, but I made two mistakes. One is I let the wings warp too much so there is a bunch of wires not perfect. More of the problem is the aileron rigging is soft. Too much flex in the system. The ailerons dont return to neutral, so you have to work them to center them. Takes a lot of attention to fly it, and most of the time its rudder turns; it would be so much better if they were working right. Did a 1/6 Fokker DVIII; major handful. I fly my Dr1 on a 52 four stroke so your 60 FX will rip the wings off if you try to fly it at full throttle. Not kidding. The old .60s on the VK plans make about as much power as a.40-45 today, except the bigger prop and the needed nose weight which helped.