Thank you for posting all your hard work ... about 5 years ago. I really enjoyed it and drooled over the speakers themselves as well. I'm hoping to run in to some older JBL's in my not too distant future.
Speaking of JBL's, I believe my little L26's grill frames are going to be a similar situation in regards to putting new cloth on them. In your cuts for the corners, I'm a little dicey as to exactly what you need. I've earmarked this page and will be returning to see if I can duplicate your efforts. I've got the orange version grill cloth to use, I can hardly wait. That color didn't stay on the Altecs, but it will for the L26's!
xo, Biggles