I am assuming you are doing kevlar truss of the Freedom Flight kit? What actually failed when you do that? I did not even add the kevlar support because I found a very light balsa motor stick that can withstand the regular rubber full winding. The balsa piece I found for motor stick was 3/16 x 3/8 x 12 inches and it weighs about .7 grams. We got down to about 3.1 grams with that motor stick.
I guess you are having a hard time getting down the 3 grams?