3 arms, 3 cartridges, one table, match them up.

Are you...
1) looking to keep one set of the three and return the other two?
2) looking for the best matching cart/arm combos for each of the three so you can mount all three in the best way?

If #1, you might ping rauliruegas.
If #2, why not try them all and then tell us what you think?

Kftool, I apologize for the original short response. I actually remember looking at your DIY TT system posting a while back and am just now remembering what it was. Rauliruegas' post had not shown up when I posted. Given what I remember of your effort (and I remember being mightily impressed - and believe it or not, your system thread with pics was one of the prompters of the idea which led me to actually take the plunge less than 36hrs ago to get an old idler wheel TT to work on (gotta start somewhere)), I would very much like to hear your impression of all the possible combinations at some point. I am frankly somewhat surprised that after the effort to design and implement your TT that you would deliberately choose to not spend the time doing a round robin and instead take consensus word for it, even though your table is a far-from-consensus table and the number of people who can offer you combined experience of these arms and carts to form that consensus is probably quite limited... I unfortunately, am not yet one, but I wish you the best in your quest.

Thanks Kftool. One reason I got the idler (also a B12H) was their re-birth and the resulting proliferation of good-natured communities who would give free advice in a pinch! One place which redoes idler wheels is Turntable Basics (without knowledge of their existence, I would have gone Thorens just to get better access to parts). I'm going to have a crack at this one before trying to get more complicated (like yours). And if the devil ever makes you decide to let go of your B12H/Grace704, feel free to drop me a line. I am pretty sure that if I manage to do a decent job on this one, I'm gonna want to do another to see if I can't do it even better...

Ken,
You've got mail.