the file_gloss was only for the aerofly 5.
There one had the texture files
For the RC7 you need
You should start with changing the file_reflection.
My model as-delphin-2 has a file wing_reflection.bmp.
With the values 255,255,255 (R,G,B) it looks like that:
With the values 20,20,20 (R,G,B) it looks like that:
If that doesn't solve your problem, you should try to change the file_specular and file_specular_alpha.