Another trick - that I personally have not tried but only read about - has to do with carpet but might be okay for this situation?? If you have seams in the shirt that you could clip some threads; make a pile about double the size of the hole. Take some glue - probably fabric type in this case (Elmer's was what was recommended in the carpet example) and make a mix of the glue and fabric clippings. Put the mixture over the hole and press. I would probably use a press cloth or piece of wax/freezer paper or both in this case. Supposedly mends the hole. Good luck!