I've been doing some research here, I've managed to get hold of an APO extender for a half sensible price (they vary in price wildly).
I'm planning to convert it to Sony A mount to use on my A77 with my R lenses
Of course, this means that I can use my R mount lenses on the A77 without having to convert them, and converting ROM lenses is an expensive operation (need to be sent to Spain)
I thought it might be worth sharing the fruits of my research
First of all the page from RG Lewis
APO Extender compatability
Of course, you also need to dial in the crop factor, so that the:
Leica R 28-90 will be a svelte 60-190 f4/5.6
Leica 180 f2.8 APO will he a 375mm f4!!
This sounds like fun.
I then had a look at David Lladó's site and confirmed with him that it just needed a standard mount:
Prices and Ordering
There are also mount fitting instructions on his site:
Fitting Leitax Mount
It'll be a while before it's all arrived and fitted, and I'll report back then. Hopefully this information will be useful to someone!
all the best