I really like the looks of this bit and I have one on order. Heard great things about it. Amazon.com: JP KORSTEEL Copper Oval Link Loose...
It should work well for a horse with a low palate.
As for the chewing thing, I much prefer my horses to be quiet on the bit. The best way I have found to encourage this is to give them something to think about other than the bit. Give them a job, keep things new and fresh, do something different.
When you are drilling the same things or performing the same maneuvers over and over, the horses get bored and start looking for ways to entertain themselves. That could manifest as nothing more than chomping the bit...or it could turn into bucking, sulling up, etc.