Assuming that the mods have made no changes to the angles between the tailplane and wing, and now the thing flies 'nose up' it would infer that whatever AOA it needed before the mod to fly straight and level has changed, and the wing needs more AOA or 'lft' than before. Perhaps the fuselage contributed quite a bit of lift prior to the mod, and cutting the tunnel has changed the amount of lift generated by the fuselage? I can't see moving a servo changing anything aerodynamically.
Evan, WB #12.