Pick up 'Secrets of shorthanded PLO' by Rolf Slotboom and Rob Hollink. There is a lot of info on playing a 20 or 40bb stack in it.
I think playing a 20bb stack is not optimal in most games.
It could be played profitably in very laggy games I guess, where you can get it in preflop or on the flop with a range that crushes your opponents (relatively as it is PLO
) and get some protection from the big stacks.
Variance can still be a bitch though as you have almost zero fold equity and have to see a showdown pretty much always.