Dang Brian, that really is a great looking Smith. I used up every piece of scrap covering in my shop for mine, looked like something out of a circus!! The reason I went to the OS .70FS was the .46 OS I had in it didn't fly the plane well enough for me. The other reason was I had the .70 on hand and it wasn't doing anything at that time. As for the ground handling with the bigger engine, I was in control of the throttle so there wasn't any great difference in how it wanted to get away from me. I'm sure Brian is correct though and the .56 may be a better choice?? I just didn't have anything smaller on hand. My Smith came out very tail heavy but it's been so long I can't remember how I set up all the gear. I did have two aileron servos though, it's just easier for me to set up two then one. The two degrees of Diff just helps the roll rate. Try flying it once without it then try it with Diff and see what you like best. I find it helps with bipes and I test most of my planes to see if they work better with it or without it, only takes a minute to change it in the radio.