The big stab gives me more stability, I'm happy pumping the 136 with the Fluid H 42 (I don't remember if I tried the 38) when launching from the dock where I can run. But it's too small for me on the 156 (I needed either the Fluid H 47 or the Sirus 50) it's not that I can't pump the 156 with the small stabs, it's that I lose efficiency with the stability "struggle". For beach start, the 50 was a big help because it gives more time to climb up.