I really love the whole Ric-O-Sound thing, but I very rarely bother to deal with two amps live - I normally just end up faking it with parallel chains from a single pick-up.
I own an old Marshal Club and Country bass amp (their sort of version of a Fender Bassman - which being open back, and intended for a clean tone, isn't top of anyone's list for thick bass tones, but it sounds great for that clanky tone, especially when you push the tubes into saturation), and that has separate inputs for the normal channel, the bright channel, and a dedicated stereo input (which is basically like when you jump the channels on an SVT, or Plexi).
Anyway, I sometimes use that in combination with a Sansamp VT Bass, with the clean link going to the normal channel, and the gritty processed VT output going to the bright channel.
I only mention that because, as far as I'm aware Chris Squire wasn't really interested in setting up the traditional Ric-O-Sound stereo chain (Bass/Neck pickup to clean bass amp, and Treble/Bridge pickup to guitar effects, and a guitar amp).
As I understand it, he had the Bass/Neck pickup going through his effects, because if he felt distortion sounded terrible on the Treble/Neck pickup, which he kept clean, and then he summed the two signals back together in mono.
I'm certain you know more about his set-up than I do, but thought it might be worth mentioning that he apparently did (everything) the opposite of the conventional way.
Please keep us updated with pictures of your finished tribute basses - and good luck learning to play the Macca left handed