This is very wierd, I added the line for building it to every generals supply center and added the objects folder but only plain old USA China and GLA can use it, it shows up grey for all others... Any ideas on how to fix that?
Yeah, unfortunately you need to make multiple copies of that same AmericaConvoy unit - airforce, laser, superweapon copies, etc in americavehicle.ini, all the other generals in their respective inis, and after that you need to change the prerequisite = line for each copy - change americasupplycenter to airf_americasupplycenter (not sure if this is the right name) for example, and you also need to find the Side = line and change it too... yeah it's tedious