In reply to climbwhenready:
Petzl website has a section on lowering off.
Their test is for a 7mm prussick ( tied triple) on a 9.7mm rope.
Tested on a 4m fall with no damage to prussick or rope.
Unfortunately they give no indication of rope out/ fall factor and limitations of using thinner ropes/thinner prussicks/bigger falls/ fall factors.
IIRC there have been fatal accidents lead rope soloing with 5mm prussicks.
Possibly David Coley has covered lowering off in his book, he may be along shortly.
In my 47 years of overambitious mind/coupled with inadequate body I have vast experience of lowering off.
Frequently gear that has held a fall, will fail on the lower, possibly because of different angles of pull between the lowering and fall situation, or maybe it just thinks it done enough already.
So be careful!