Hi all,
I'm coming late to this discussion but I wanted to add my experience to the discussion. I just installed a JLD Bridge Doctor screw mount version into my 1970's vintage Penco A14M (made by Ibanez I've learned). Over the years it has bellied pretty badly causing the intonation to be off and the action to rise.
It's not worth a lot except to me for sentimental reasons (gift from my finance now my wife of 45 years).
I decided to try the JLD Bridge Doctor because it was inexpensive and I had nothing to loose if it didn't work the guitar was doomed to become wall art. Well it worked very well for my situation, the top bulge and tilted bridge are much improved and the intonation is also nearly perfect now. I cannot verify any of their claims of improved tonality or volume, but I like the way it plays now. Well worth the money and the afternoon I spent installing it.
Cheers,
John