theres a reason we use two batteries often!
depends on the glowplugs you use too, 6V plugs like bosch work FANTASTIC on a pushbutton setup but are easy to burn out because they get so hot so the controller will kill them, so its 100% a no-go with the controller. The motorcraft berus in my SWAG run cooler and thus can take more abuse from the controller. My old blown out engine would start great on bosch, and barely on beru. I've heard OK things about wellman, but again I would only use motorcraft beru with a controller. Pushbutton opens a whole new world.
Gotta remember how old these GPC are, the technology in them isn't very advanced at all...