So I figured why not hack the cheap ebay light to get it to work? I took out one of the four emitters (thus knocking it down to two as they are wired in pairs internally), and now it was drawing about 4 watts. Still tripped up the protection circuit (if there is one) internal to the motor controller.
Bottom line is that the new controller loses its mind with 4 watts, so if you are designing a light to work with the rad product, you need to feed it from a fused line from the battery tray, and just use the light circuit from the controller as a sense line. Not difficult, but maybe above your average Joe to install as soldering and tinkering would be involved. Dunno. The other possiblity is I have a defective controller, or the one that was original was exceptionally robust. Same part number.
With the OEM light, the controller works fine, so that's where I am at now. Might just get a self contained light and be dome with it.
https://www.amazon.com/gp/product/B01IO12B30/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=ATVPDKIKX0DER