Oh wow, that second one is particularly effective!
I've often considered doing horse holders like this, but hadn't considered that I'd need to resculpt the reins and create stirrups as well...
I don't think I'm going to do it in the end, seems beyond my skills, but I applaud you for doing it!
I've used the same Agincourt metal horses in walking poses for my own mounted crossbowmen (as yet unpainted). As you've found they scale well with the metal WOTR horses, but are definitely noticeably smaller than the plastic WOTR horses. Work very well for mounted longbowmen/crossbowmen!
(Though if a certain company ever decided to release packs of horse holders I'd buy a load of them....)