Ms. Mum,
I guess I'd just get up on that horse and start riding. What's the worst thing that can happen? See, not so bad.
Of course the horse isn't going to mind. Only you will mind if you should spring a leak. I've only been an ostomate for five yeas now and have yet to have an "explosive" leak. But I have found some things that do seem to help keep the wafer attached when sitting down a lot. And in a saddle you are, basically, sitting down. The belt? What kind of belt are you referring to? I use the belt supplied by the ostomy companies that attach directly to the wafer. They seem to keep the wafer attached even when it "breaks loose" due to some weird occurence. Those things that allow you to put the bag into a thing that wraps around your waist are, in my opinion, a WASTE! they do nothing. Oh, wait, they do make my more sweaty! So, go give that little horsie some fun and see how he (she?) and YOU like it. I ride bicycles and motorcycles and the only real trouble I've ever had is sitting in my truck. But it's never caused the bag or wafer to come "unstuck". I've used a lot of different bags and companies and can always give you MY reccomendations. There is, in fact, a product that I tried (and it stuck really REALLY well) that is also recommended for climbers and skin divers. Cymed, I think. Google is your best resource.
Say, is your husband Japanese? I would have tried to convince him (if he were MY husband) to retire in Japan, but that's just me, eh?
NT
Oh, by the way, I can be reached most easily at my normal address which is ntrubov at swbell dot net.