Well, I finally put this together. Works very well, although that is what everyone predicted. Hardest part of the job was finding a place for the Run/Program switch. Did not realize that the fuel tanks on the WBB GP-9 are full of steel weights!
I started out with the motors in parallel, and after that worked successfully I changed them to series just to see what terrible things would happen. Nothing terrible happened, minimum speed was a bit lower so I left the motors in series; the lower current on the Cruise Lite was an added benefit. Added a 1.85A PTC fuse to the motor circuit.
As an aside, I also purchased a Sound Converter; sounds are not important to me but I thought it would be nice to have the whistle/horn. Learned that the standard cable supplied with the Sound Converter does not match the connector on the Cruise Lite. Spoke to ERR about a solution and we are kicking around a couple ideas.
All in all, a successful project. Cruise control in TMCC is impressive, but the minimum speed in conventional is still somewhat high. Will add some electro-couplers when I get up the gumption!