Hi Keefer,
Maybe a little southern advice might create some thoughts?
First the Giles is a straight forward airplane design, should have no quirks
That so, if the airframe is true in all respects then flight should be fine.
What does the above say?
Considering the smallest detail> closely check the entire airframe for
trueness.
Wing and tail is square to center line?
Wing and tail incidences are correct?
Flight surfaces are warp free?
Fuselage is true about the center line?
Fore and aft balance is proper as well as lateral?
Thrust line is paralell to line of flight?
Vertical C.G. is close to thrust line?
As you go through this list more may come to mind, do not hesitate
follow through.
Quite often we can not see the tree because of the forest but going back
to basics carefully often the culprit will be obvious.
Good luck and have fun!

Hal [email protected]