Just what everyone wants to see... another bit question?

I like your options, they're much nicer. I would personally go with the double jointed bit (it is not a french link though, it's simply a double jointed bit with a roller). Double jointed bits are a little more difficult for a horse to lean on and grab, but gentler, because they don't offer the cracking effect a single jointed snaffle does. A double jointed bit acts more on the bars of the horse's mouth, rather than pushing up into the palette. The sweet iron is not a bad choice either but if you already know how he goes in a snaffle I don't think that'll change much, same for the D-ring with rollers.

(Editing in a second.)

Sorry about that, I had to go deliver a cat. xD

ANYWAY.

Here's a couple of choices I would also suggest.

http://www.horse.com/item/jp-oval-mouth-loose-ring... - Doesn't have the 8 figure like a french link, and this style is meant to conform to the bars and be even softer in the mouth than a regular double jointed.

http://www.horse.com/item/korsteel-sweet-iron-fren... - Sweet iron + french link. Horray.

I like loose rings because it enables the bit to move around in the mouth more, making a mild bit even better. If he's having trouble on the whoa in a soft bit -- I'm sure you expected to hear it -- he could probably use some more work on respecting your signals.

ETA: Ahhh okay, then I misread it, haha. I thought that you'd had him in snaffles before and he had trouble stopping. I don't know WHY or HOW I read it that way now that I reread your post... I think I had a real brainfart moment there or something.

Just as an experimental see-how-he-does sort of thing, you could first try him in a simple snaffle and determine what he would need from there to work him down to a nice, soft bit. I dunno really, just throwing out ideas at this point. He's used to the snaffle action on the Kimberwick so for an easy, slow transition from bit to bit that might be where I start. Just changing a few things about the bit at a time instead of throwing him on something totally different all at once.

The egg-butt roller should ideally keep his mind on the bit, to play with the roller he has to know it's there and pay attention to it (eventually this becomes second nature to some horses though). It'd be a good bit for transitioning to double jointed instead of just throwing him in an oval link or something else that would be really weird to him.

ETA!!!!!: Just got to AB's post and I have that bit. I had been using a straight rubber bar bit ( http://www.horse.com/item/korsteel-solid-rubber-mo... ) on one of my mares for a while and she didn't seem to have any problems so I immediately put her in that. The confusion was immediate and she was basically looking at me like, "WHOA WHAT THIS???" but after literally just a few minutes she had the idea. It was very nice. Her reactions to even super subtle signals were superb. I did do all of her work on the ground first while introducing it though so in that circumstance I would really recommend the same thing (like long reining), just in case something DID happen you wouldn't be in a terribly bad position.

With the rings/cheeks, if you want more responsive steering go with a full cheek. A D ring and an eggbutt have the same effect on the horse's mouth. A loose ring will stop a horse from bracing against your hands/grabbing the bit/not listening to your commands.

I feel as if the "Korsteel Copper Roller Eggbutt Snaffle" would be tooo easy on your horse's mouth. After all, you still want control.

Instead, think about getting a french link snaffle like this one. It gives you a little more control than a snaffle. Only downside is that it's not appropriate for hunters, I believe.

http://www.horse.com/item/korsteel-french-link-egg...

^It's great for everyday use.

Before you go out and buy a bit, why not convert his current bit to a snaffle? Just attach the cheek pieces of the bridle to the large D rings of the bit, take off the curb chain, and you have a simple D ring snaffle. Give it a try.

If you want to buy a bit, I'd recommend a simple full cheek snaffle or full cheek french link snaffle, both with keepers. He's used to responding to poll pressure with this bit (or any leverage bit), and if you use your full cheek with keepers it will produce a very light poll pressure. He'll find this familiar and comforting, even though it's much less than he's used to.

But I'd try him in his current bit, reconnected to act like a snaffle, first. It'll give you a better idea how he'll respond, and if you need a stronger or milder snaffle.

the bit you have is like a snaffle it just has a different leverage and a chain, to step down to an easier but try a d ring or an egg butt snaffle there alot easier going and do not have as much leverage in the horses mouth and he should be able to transition into it nicely

I've never seen a full cheek on a western bridle (I think you ride western because you talk about shanks). I would go for a simple loose-ring single jointed snaffle.