Hokay so, I work at a tack store and honestly for all the pairs of boots we zip up on people weekly, tight and tall, we don’t have zipper malfunctions and nor do our customers. Although, many times our new employees don’t know which boots can take more strain than others.
I have 2 pairs of Ariats and hope to get a 3rd this spring/summer when their new dressage boots are out and they are the zippers we can force up the most. My Volants are skin tight but because Ariat has re-done their zippers and put stretch panels along side them, they can take a beating. You will also notice that the materials are not the same. The leather is softer and more pliable out of the box compared to the old pull-ons.
I have a pair of pull on dress boots with boning up the back that I would love to put zippers in but it’s about placement. I would have to put it up the inside so that there is less stress put on the zipper.
I also have a pair of mountain horses that have already had to have a new slide put on because it stretched and popped right off. They are nice but not nearly as snug as my Ariats, nor do I think they could be. They make a very hearty every day boot as the leather is thick and stiff and durable. I polish them regularly and wipe them off after my rides with a damp rag and never hose my horse in them and they will last a long time.
Honestly, the worst zippers I’ve had the pleasure of working with have been the treadstep zippers. I have gotten those stuck on a customer before because the zipper blew without even trying to force it.
I also havent been impressed with der dau’s or sergio’s zippers either, for expensive custom boots the zippers look like they belong on a kids jacket.
My biggest suggestion for getting a custom or semi-custom boot is going to be make sure to get the stretch panel and gusset (the little stretchy triangle on the inside of the leg at the knee) if you’re going to get zippers.