Bentparts,
You stated that you did a test drive with your homemade 1/2" driveshaft spacer and encountered serious vibrations. Next you tried a bigger spacer from Rocky Road, problem solved. What do you mean by a bigger spacer? Diameter, thickness? What size is the spacer you are running now? I assume this is an aluminum spacer.
I have never had much faith in driveshaft spacers, although I have never run any either. On all the suspension lifts I have done I always measure the slip yoke position in the transfer case before and after the lift. Then I take the driveshafts to Bay City Joint, Clutch and Gear (local shop about 30 miles south of me) and have them lengthen the driveshafts. They do this by cutting the old tube out, at the welds on the u-joint. They then weld in a new tube that is of the correct length (longer). This shop even has the capability to spin balance the shafts. They weld on weights to the tube. You get back a proffesionally balanced shaft. It has been a couple of years since I have had a shaft lengthened, but at the time it was well under $200 dollars a shaft. It is actually less than that if you deduct the cost of new bolts and cost of the spacer. Confidence in your equipment has got to be worth something too.
Sincerely,
Nine Pine