What is the standard length LP hose for going between 1st and 2nd stage?
JOHN P Over time they have varied somewhat from different manufacturers, but usually 24 to 28 inches is the normal 2nd stage length. The longer ones will be a little less likely to tug to the side which you may find to be more comfortable, especially on longer dives. I normally use my longer octopus hose on my primary with the normal length hose on my secondary just below it on a neck strap - a leftover habit from my cave diving days.
BRADLEY M 27" is standard, 36' if you are tall and girthy (plump) and want more hose hanging down so you can see it easier
Underarm 40-44" again depending on your size.