I was then told that mullen mouths aren't typically used because they're severe. This was a shocker to me, I always saw them as pretty darn nice compared to single jointed snaffles.
Can anyone explain to me what makes a mullen mouth bit so severe? Or a bit with a low port (not the higher ports that hit the pallet). Right now I'm using a low wide port kimberwick with the reins on the snaffle ring with no curb strap for my Belgian, he goes very well in it - which is why I was looking to simplify it with just a mullen mouth snaffle. But if it's harsh maybe I want to look for something gentler if he'll be as comfortable. But I just can't picture what would be harsh about it.
I could see maybe a french link being softer, maybe? Or one of the mylers mullened out double jointed snaffles that have the bar to prevent the nut cracker affect. But a straight single jointed one I just can't picture. She recommended a Waterford - but I think my guy is simple and all that movement in his mouth would drive him nuts.
He used to go in a single jointed liverpool with the reins on the third loop down, that was for driving in the city - but single joints drive him nuts, if given the opportunity he gapes his mouth and leans into it - so it must be hitting his pallet. With the wide low port bit I'm using now he packs it comfortably and doesn't fuss or gape his mouth (we don't even use a nose band - couldn't find one to fit his big mug!)
If anyone can provide some science I'd love to hear it! Maybe I've been wrong all along.