I going to put couplers on a second bike. I have a Dean Ti with S&S BTCs. Rock solid downhill at speed, pulling a trailer, indistinguishable from a non-coupled bike, but the couplers are big and heavy.

Reports of riders using Ritchey Breakaway and Dahon Allegro bikes are generally positive about the BAB couplers on those bikes, which add only about 100 grams per coupler. Some report that the lower coupler threads can easily be stripped (so carry a spare coupler) ... and some riders report having to retighten the coupler during a day's ride. I can live with these shortcomings for the tradeoff in weight.

Any other opinions of S&S vs. BAB couplers?

Does anyone know of a source for BAB couplers?

As a reflection on the deficiencies in the BAB technology, Dahon has introduced Interloc(k) Joint Techology, in which a tongue extends into the abutting tube. IJT will only be available (so far) on the Fuego (MTB) ... TMK not yet shipping.