Hello Carter.
I think that most things have already been said, but here goes with my own perspective:
I spent a while with the stoma nurses discussing the location options and preferences. My main consideration was the beltline, which I did not want to be interfering with the stoma. I opted for a couple of inches below the beltline for that reason. However, what I found in practice was that, over the day, my trousers tended to drift downwards, ending up as hipsters, which rather defeated the choice of placement. At first, I resolved this by wearing braces to keep my beltline in the right place,but it still posed problems when I was bending over and the belt dragged across the stoma. Eventually, I decided that the best option was to wear one-piece overalls (what we call 'boiler-suits') which do not need a beltline at all. These work very well for me and have the added advantage of making it look as if I work for a living! They are also useful in terms of getting free access to the stoma for changing appliances without having to disrobe.
I have designed for myself, a proper suit with a waistcoat, which attaches to the trousers and thus holds them in the 'right' position. However, as I rarely have any need for such a thing, it has never been made, so I don't really know if it would work in practice!
If I had to choose a different place for my stoma, I do believe that I would have just as much trouble deciding now, as I did at the beginning.
Sorry if this is no help to you whatsoever, but it does indicate that you are not alone in struggling with making these sorts of choices.
Best wishes
Bill