Well I don't think it was the prop that caused your trouble. Although you can get some speed from an 11x7 thats for sure.
Unless it was way out of balance. I also noticed in the pic that you used the stock wooden push rods,, they are weak. Also noticed they aren't wrapped or have any heat shrinking where the metal rods attach. It wouldn't have been long till those failed anyway.
The wing saddles are very weak. Same as the Seagull models. In fact,, they are basically one in the same. Same wood, hardware, covering,, everything. Even the manuals are printed the same. Except the name. It's no wonder,, they are both made in the same factory in VietNam or someplace similar. One is sold by Horizon , the other by Tower. Half the hardware and even the landing gear I'm using came from my crashed Seagull Extra300. But with a little reinforcement during the build they hold up pretty well. Even when over sped.
This little plane (Giles) looks fast. Should be fun doing vertical lines. I'll just remember your pics and chop the throttle on the down lines. At these prices I'm sure many will sell. It's good to have referrance like this.