Your tank is just a little smaller in volume than mine is (viewtopic.php?f=4&t=67694), but the footprint is better, so you could do something similar to what I've done.
My demis and yellows are still growing, but the best thing to do with demis especially, is to get them as juvies in a group up to twice what your adult stocking will be, and then take out the aggro ones when they get older.
I've got around 25 demi juvies and 15 yellow juvies at the moment, plus 10 adult rustys (plus fry), and a group of cuckoo catfish.