Ok, you try this at home at your own risk!
But this is what I do to 'help' the current model of Gloves fit my horse's wider than long hooves (in front).
The size of the problem. A 1.5 Glove is 3mm too narrow and 5-6 mm too long. Neither a size 1.0 or 2.0 work at all.
A Bare is a slightly better fit, but really I ought to go for an Old Mac (only I really dislike them. That is Really Really dislike them.) They are clumpy, go too high on the hoof and are a PITA to get on.
So as I hope the Gloves are only a temporary measure at any time I do this:-
For a new Glove fit when warm (a dunk in hot water will do the trick on cold days). Make sure hoof is freshly trimmed and that there are no unnecessary sticking out bits on the width. From the forward section of the quarter (where the hoof starts to narrow for the toe) put on a good quality duck tape. (Sorry US peeps but the stuff I got from Walmart is pants. For best effect use the 'proper' duck tape which is a tiny bit more expensive but not much.) And if the front of the boot is gaping at all then fit Power Straps. Then if you have a rasp to hand bring the breakover of the boot back a little. Enough to be effective, not so much you drastically shorten the life of the boot. (One of the reasons too long boots come off so easily is the horse can not make their natural break over so they step on the back of the fronts.)
If you have a problem with back boots coming off then double check the fit, width is important as horses often 'screw' the hind foot so the boot can twist off. If your boot fits well but there is a lot of twisting action then duck tape on the hoof wall works well. Remember use the good quality stuff that really sticks and grips.
The only problem with these measures is then getting the boots off............
Remember folks - at your own risk! :-) But it works for me most of the time.