Anyone have experience with the Lingenfelter aluminum driveshaft?

I still have some vibration at speed on the interstate. My driveshaft was loose at the rearend, so I had it rebuilt with 373 gears and new bearings. I then discovered my driveshaft was bent (probably what caused the pinion bearings to go out), so I bought the LPE driveshaft. Then I found that my tires were out of round and they were almost to the wear bars anyway, so I replaced them. It is much better than before, but there is still some vibration.

The LPE driveshaft is balanced with weights, but it also does not spin true. When I'm under the car with the driveshaft turning, it is out of round. Or, more accurately, it looks as though the shaft center does not match the center of the yokes. Could this be the problem? Anyone else notice this with their driveshaft?

I also rotated tires front to back, with no difference. The vibration is through the seats, not the steering wheel.

 

I have no problems with my LPE ds. If you really suspect its not right, you should be able to get it checked I guess, but I'm not sure who could do that.