Nice setup!!
I really like radios (or any electronic gear) that has been racked and stacked!
The mini rack you have there looks very good- and makes the whole setup easily portable.
I am probably going to do the same with my UBC780's and BCD996T since they are very similar width.
Did you build them from a kit or were they already assembled?
The multicouplers are more items that I need to obtain- too many radio's and not enough antenna's. I need real ones (Stridsberg's) as I have already gone down the TV splitter road and they do not exhibit enough isolation between scanners.
As far as adapters go- I always try to avoid using them- especially above 400Mhz, but if the signals you want to hear are fairly local to you, then they will do a good job without noticable signal loss.
Regards, Commscanaus