Just remember:

The horizontal stabilizers on the Phantom II droop 23.25 degrees.

Dry fit the pieces till you get the right feeling; you may have to sand the pieces to fit the stabilizers to the fuselage in the best way possible. Once you have that correct, use crazy glue or any other cyanide-acrylate adhesive to have a fast dry. The resulting gaps may be filled with the same crazy glue or putty/filler, sand away excess and presto.

If Elm's answer doesn't work, then a picture or two would be helpful.

Regardless of the quality of the kit, I ALWAYS prefit my parts as I build. Do not be afraid to take a blade or file to something to smooth it out to get it to fit. Keep in mine these are mass produced kits and over time there will be some changes in the original mold. Before you get much further and have to unglue things ( there is a solution you can use to release the glue, have used it my self. Becarefull, it will make the parts a little brittle) make sure the parts you are using, fit to where they need to be. It is the cardinal rule in kit construction.
Revells Schnellboote S-100 being converted for R/C use. Note the battery charging port being placed under an air intake.

Damn, guess they changed how one is suppose to post a photo, what is the code now?

Can only put pics in first post :(