I know the answer, but figured I'd gripe about it anyway.
I've used up all my licenses trying to get an HPT that would work with my DBW system.
Turns out that none of them fixed my issue, and I think I've figured out the problem.
So, now I found a vehicle that I'm almost 100% sure will make it work right, but in order to even try to see if it will work, I need to buy more credits.
There really should be a way to test things in this manner without burning up credits for things that are of no use to me anymore.