You are fine, and don´t worry about the pitch trim, as the elevator response on the F-15 is very soft and nice.

Presuming your CGis about on the right spot ( indicated by the manual) this stab position will make you fly straight and level at cruising speed. Of course, right after takeoff you will need to hold a little "up"stick until the speed builds up... meanwhile you may concentrate in triming the aleirons wich are must faster in response than the elevators. Aspotter may be helpful for doing this at the maiden flight.

Good luck with the maiden, and if possible send us a video so Juninho can enjoy it too! :-)