I was going to mention having the wings on when running too. They dampen a lot of the motion that's concerning you. More will go away as you get some time on the engine and carb settings are closer to what you'll actually be running long term. The extra tail brace wires won't hurt a thing though!

I agree also that time spent ground tuning/running (beyond what is required for a basic tune) is generally not necessary. The best ground tune available will still very likely need to be tweaked when it's actually flown. I get it though if this step is more of a confidence builder!

Regarding your ground clearance issue, you could narrow your gear up a bit to gain some, and look around to see if you can find a tail gear with a little lower profile?