actually, using flams with different velocity levels work best in most cases because you'd want to trigger two different samples for the two different hits (two different samples of the same drum of course). if you have two loud samples of the same snare drum, you can actually use both for the flam, coz using two loud samples for a flam also has a sound of its own. in general i use 1/128 or 1/64triplet for flams.
the two commonly used flams are (1) one in which the first hit is softer than the second one -- i hear this kind from peter erskine a lot, and (2) one in which both hits are generally of the same dynamic level -- a favorite for rockers.
if you want your drum loop to sound as 'real' as possible, you wouldn't want to trigger the same sample consecutively. it's what's termed as the 'machine-gun effect'. nothing wrong with it, especially if you want your drums to sound like the music of the 80's.
