Just use T pins to hold it against the balsa side, that will hold it until dry, although you say you are allergic to CA. have you tried using carpenters glue or whichever you use, on the triangle stock, but leave just about a 1/16 of an inch here and there without glue, and here put a drop of slow Ca., that works very fast and you get no fumes, as long as you apply the drop of Ca. towards the center of the triangle stock.