Thought I would jump in here and tell you about
DH's situation although not identical to yours. DH has two abdominal fistulas located a little over an inch apart. He utilizes ostomy supplies rather than wound pouches for a variety of reasons. He also had numerous peaks and valleys on his stomach due to multiple surgeries and as you know this creates a nightmare trying to get anything to stick to an uneven surface. He has always had short wear times, 24 to 36 hours max and many, many leaks and blowouts. Several months ago, I saw Tincture of Benzoin mentioned in a post, as being of help in these type situations. Stuff is cheap, $5, bought a bottle on Amazon and DH tried it. At first he didn't think it was going to help as it didn't appear to be sticky at all when first applied. My thought was that it was the cheapest thing we had tried at least! A few days later, DH said I think we may be onto something with this stuff, it isn't sticky when first applied, but is very sticky within a couple of minutes. He is using it regularly now, just ordered another bottle. His leaks were almost always at the bottom of the flange where he has a rather deep crevice. No matter how much, or how little, product he tried to fill the crevice with, his drainage would seep under, or eat it's way through. Now he puts a few drops of the Tincture of Benzoin on a waxed paper, dabs a Qtip into it and applies it to the crevice before putting the other adhesive product in it. Regularly getting 48 hours of wear time now. Still not great, but I don't believe folks with fistulas are ever going to get the wear time an ostomate does with a stoma...just isn't going to happen. This little bottle of stuff has changed our lives. In the several months he has been using it, he has only had 2-3 leaks...none massive in nature. We have not had to change plans at the last minute or leave an outing in a hurry because of a blow out. Previously, he would get so frustrated and depressed over the constant leaking and changing, and of course the constant pulling off the product that would stick was terribly hard on his skin which in turn caused more issues.
Just thought I would throw this out there for your consideration. As I said, it's only $5 and if you are utilizing wound pouches, you know that cost is nothing in comparison to what a pouch sytem of any kind costs.
I wish you well!