I gave my sukhoi ( with an inverted 4 st) 2 washers down and right thrust. that is to say no washer on the bottom right, 2 on the diaganals and 4 at the top left point. If you kept the 45deg down mounting that is stock then 2 at the bottom of the engine will do. In any case the setup I have on mine trims nice n and straight .

To tell you the truth I let my friend do the maiden, at the time I was not confident of my abilities. I didnt need much trim, some up elevator as I recall. Moine lands a bit fast but is managable.

I would make the changes if i were you. Ive botched engine mounting before, a bit of a pita but no big deal. I dont know about the giles ( i havnt assembled mine yet) but the cheesy engine firewall screws on the sukhoi were too short with washers so i bought some nice chrome 3 mm socket head screws. These planes are kinda heavy but they are tough, Ive made some crappy landings and only bent the lg. Other planes would have come apart.
What engine did you use?