Have not used the IBS when boarding -- just the KGB and about 350lbs in each rear locker. The 205v/X2/X1 hull throws a mean wake for boarding with the basic stock ballast.
For surfing I use IBS, KGB, and 750lbs on port side, plus a couple of people on port side.
"For every complex problem there is an answer that is clear, simple, and wrong." (Henry Louis Mencken)
2005 X2, Viper Red, MCX, Acme 1285, PPass, rear 750 sacs, KGB, IBS
(previous) 2001 X5, 1991 TriStar 190