I've been down this road. When it is in for the balance, the machine they use for the roadforce should be a Hunter GSP9700. It is an excellent machine when used correctly. The problem is 95% of the shops don't use the machine to its designed potential. The machine will tell you the roadforce in lbs. for the tire. There is an acceptable limit, and after that the tire is considered bad. I always watch them do my tires, so I can see for myself if the tires are bad, and if they use the machine correctly. I forget the exact number. I bought a set of BFG AT's for a 4Runner a while back and two of the four had to be sent back to the factory.
The thing that this machine will do that most tire shops won't "waste time" on, is that this machine will tell you exactly where to rotate the tire on the rim to give the best ride and least amount of weight. It measures tire and rim runout, uniformity of the tire, and other radial-force related problems. To do this though, they need to mount-balance on machine-dismount-remount in the correct position on the rim-rebalance on machine. It is a pain for the shops, but it is the only way to get vibe free. Most new cars come from the factory mounted using this method. They don't want to loose a sale from a test drive with a car with easily and cheaply solved vibration problems.
You are halfway there by using the Haweka adapter (it mounts the tire to the balancing machine using the lugholes, not the center hole in the rim) and roadforce machine. Just make sure they are using the machine the way Hunter designed it to be used. Sometimes you need to be persistant. Good luck. Here is more info on the machine:
http://www.hunter.com/pub/product/balancer/4159T/index.htm
PS- Awsome truck, by the way!
