I am on to plan B. Rather than using 3 Cruise Ms I will try a Cruise M in the original powered A and a Cruise Commander in the other A unit also powering the B unit. Not ideal with two radio boards but hoping to get them running close with the nudge feature.
Intial testing with the single Cruise M powering all three units (6 motors) showed intermittent current peaks over 5 amps. Way to close to max especially given they were running light. The engines have little run time so also hoping some break in miles will reduce current demand.
Pete