The control rods that work great and aren't affected by temperature are Sullivan Composite Rods. Tower Hobbies http://www2.towerhobbies.com/cgi-bin...?&I=LXFV42&P=0

Another way to strengthen the fin is to attach 'flying wires". The easy way on this type of model is to use weed wacker line. Drill a hole , the diam. of the line, through the fin near the top and forward . Drill a hole in each side of the stab about 2/3 +- out from the fin. Drill these holes at a slight angle. Put the line through the fin and CA in place. Pull the lines through the stab and making sure the fin is 90 degrees CA in place. Snip off the excess line at bottom of stab. I've done this on the LT-40 and LT-25.