My nephew & I both have the h-9 edge with fox 3.2 engines, I havent flown mine yet but he has, & it is a good 3der, just have to keep a little power on when landing, the use of spoilerons helps a little with the tip stalling. he has hitec 625s on all his surfaces & it does good so your 645s should be ok just a little slower. I have 5945 digitals on all surfaces, I know its overkill but I am getting a good stock of them to put in a 40% bird in the near future. I think all what you are planing will be ok just do some beefing up on the firewall & landing gear block. we are running 20x10 props & have sufficient clearance. I have the carbon fiber gear & it gives a little better clearance the the stock alluminum gear.
Good luck
Gil