I have used both 2100 and a 2200 mah packs with my Seawind EP and both fly great but you end up with a very conservative CG. I got something on the order of 15 minutes of flying with the 2200 and still had 600 mah left. The lighter packs come into play when you want to get off the water quickly, but the larger packs work well as long as you're not fighting too much chop.

Bob