Kevin,
I don't know about the Extra 300 that you have but I have the 45% Cap 232 (ex Ali Machinshi that he displayed at Sandown etc). Its a fantastic plane. the wing is foam internally with a large aluninium tube as a spar so sounds similiar in construction. Ali did over 200 flights with it and if anything was going to break it would have done it by now. Why don't you speak to IAD for reassurance.
John