The wing makes the trainer. As long as you don't alter the wing, (and its alignment to the tail surfaces) you can almost reshape the fuselage at will.

Start with a basic Tower Trainer 40 or equivilent. Chop the upper fuselage down to make it shoulder wing. Don't join the back end of the fuselage, make wider formers to keep the same width all the way back. Now cut 2 inch thick foam profilew from the wing LE to back of the fuselage. BNevel the front of those profiles top to bottom at 45 deg, to simulate a jet intake. Make two 60% size rudders and fins and chop the horizontal stab in half. Cut a 1/4 inch slot in the stab halves for a spruce spar on the 25% MAC line ( about 25% of the stab area forward, and 75% aft of the line close is good enough.) the same distance from the back of the plane, as fronm the back of the stab, cut a slot for the spruce 1/4 square stock. Get 1 1/4 inch TE stock and make a new elevator full width. The fins will mount on the edges of the fuselage, where the stab halves meet it. Add canopy and you now have a sorta F-14.