And you do that how? I don't recall there being anything on the lens to indicate infinity?
Is there much advantage of reversing over extension tubes other than the available light needed? I see you mentioned compact size too.
This symbol, should be on all your lenses.
Thats bout it, extensions dont really worsen IQ as theres no extra glass. Could say thats all, but the light thing makes a big difference as with most photography and lenses.