Hmmm. Pull-ups don't work to well for messes. I've had IBS for as long as I can remember and if you are looking for protection I recommend a diaper with a inner leak guard. Some of the better pull-ups do have leak guards. The problem with pull-ups in general is they, well, pull up and, if they get the least bit heavy, don't stay up. Molicare, Abena, Northshore and Tena make an intermediate diaper and I believe most of them have the inner leak guard. You can always add a pair of plastic, nylon or PUL pants over the diaper that will help contain an accident until you can get changed.
I gravitate toward the most premium diaper I can afford due to my OAB and IBS, but there are times I really want a lighter version so I know what you are trying to find. The problem I have with this search is that when you find that lighter diaper and start wearing it, if you are the least bit IC, you inevitably run into situations when you wish you had more protection than you do. Been there and done that.