I would check the spar tube length. I had a similiar problem with a set wings from a different model. Slide the tube into each stab separately and make some pencil marks on the tube were they bottom out. Now reassemble on the fuselage. If the stabs are making it to the marks you made but you still have a gap, shorten the spar tube just slightly more that the total gap. Use a tubing cutter to make a clean cut without distorting the shape of the tube. I took about 1/4" off of my wing spar if I remember correctly.

Whats causes this problem is two things: either the spar is slightly to long, or more than likely, there a gob of glue that seeped into the end of the tube socket during assembly.

Hope this solves you problem...

Mike