I will give you my humble 2 cents. Sabots can come in different lengths - depending on the weight of the bullet.
I am not sure that cutting the wings is a good ideal, the tip of the wing is specially designed to move away from the bullet at a given rate all the way around.
If you order bullets and sabots together you certainly will get the right sabots, but that is the expensive way to go. I myself buy boxes of bullets and then purchase sabots to fit my rifle - not all sabots will go down every rifle, unlike center fire barrels there is no such standard for muzzloader barrels, therefore they do vary.
One example I will give you is that I use TC Mag sabots and I often short a shorter 240 grain XTP - the sabot is longer than the bullet and it does shoot very well.
One thing with any muzzleloader - experiment - eperiment you will find your right combination - what works really well for me might not work for you...