I installed the IBS on my X2 this summer. I just left the starboard overflow hose attached to the thru-hull and cut it just above floor level and attached it to the sac. If I ever want to return it to stock I just need to insert a coupler at the cut point with two clamps and it's back to original. Took me all of 2 minutes.
And ya, you'll only get 300 lbs or so. The cup holders will pop up too -- that's how you know it's full!
"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