I've used Old Mac's G2 hoof boots on and off for a number of years. As Brena's pigeon-toed front hooves wear quite unevenly on the stonier trails around here, I've been using the boots more often. They had tended to come off a lot until I sought the help of a new farrier who shaped her feet better rather than letting flares become excessive.
Old Mac's G2 boots work best when a foot is about 5mm longer than it is wide. So I had to make a modification given that Brena's front feet are quite long compared to their width. The heel strap wasn't quite long enough so insufficient Velcro overlapped to keep each boot secure. I attached another D-ring to the one that is fixed to the boot, which enables more Velcro to overlap. The connection is formed of two cable ties each looped around twice, and experience has shown that this is strong enough.
This does differ from the manufacturer's advice, which is to buy a bigger boot. However I seem to be using a boot that is the right length, as Brena's heels don't sit over the back of the boot (as I discovered they do with Easyboots). There must be other barefoot horses around that are hard to fit boots to, and I wonder what their owners do.
These boots are several years old and have seen a lot of use. The rivets securing the upper and lower parts together at the front have begun to corrode. After several rivets failed, and before the boots came apart in use, I replaced these with bolted connections, using washers to replicate the rivets' coverage of the plastic boot structure. On the boot pictured, I've replaced the lower two rivets. The heads of the screws are inside, and these are domed so that the hooves aren't abraded.
These repairs have also proven effective. Again, this isn't a recommended course of action, however I don't want to retire a £90 boot when it has a fair amount of life remaining in its tread and upper part.
I had thought of trying to rivet the connection, however a saddler reckoned that he'd struggle to get a riveting tool into the cramped toe area. It was hard enough working with a small screwdriver and pliers.