6 inch blocks in the rear gave me bad driveline vibration on acceleration from 0 to 10mph. Shimmed the carrier bearing 1.5 inches in 1/4" increments this morning. I have reduced the chatter to a very minimum. Is there a problem with shimming this much? I bet I can get rid of the chatter alltogether with one more 1/4" shim but that might put strain on the carrier bearing (it will hand at an angle). Any ideas or suggestions?

The only problem you will have after it drop a lot is that the shim will need to be angled front to back. You probably noticed it started putting the hanger bearing in a bind. This could cause premature failure in the hanger bearing. I would have said this before but I didn't think you would have to shim it that far. If I remember I usually angle the drop at 2" or more. No science to it though. If it looks like to much of a bind, angle it, if not, don't worry about it. As for other reasons not to drop it that far, I don't know of any. Never seen anyone have a problem with them.