best way i find to do it , is to layup a set of exact size window frames in photoshop etc etc, and print them at exact scale onto thick card or paper, with the paper ones i then stick them to thin ( .20) plastikard with a little liuid poly then with a sharp scapel and a ruler cut them out, remember do the inside first or you will bend all the frames. this gives you a perfect frame, I do this for nearly every frame job i need too.. I did just post a set of frames on the forum last night actually for the Deans Marine Whaleback. If you can give me the exact measurements for the frames I may be able to run you up a template set too ? I use formula 560 canopy glue to glue mine in , it dries clear and is neat and very sticky !