For 3/4" I might put a leather covered pad on it. I did one, but the pad is actually a very firm (almost hard) closed-cell foam, which adds almost no weight. I think I got it from Brown Precision, they used to use it (uncovered) on their synthetic stocked Mtn. rifles. Not sure if it is still avail.

Anything longer that an inch or 1 1/4", and I think a wood extension looks much better.