A french link shouldn't touch the pallet either.. he should be fine in it.
That much foam is NEVER a good sign, yes some foam is good, but it should only be like a tiny bit of white lipstick. Any more and it is a sign of the horse being stressed.
Instead of just looking at the bit, try to examine his whole environment and find out if there is anything that could be causing his anxiety. A horse that chomps the bit so vigorously that there is foam streaming from his mouth is obviously under a great deal of stress and discomfort. Check saddle fit, have a soundness exam, etc, etc. You really want to try to eliminate any stressors in the horse's environment.
French links provide good tongue room, so this should help if your horse has a large tongue (like my Dan). I had a JP Fench link with a curved mouthpiece which worked really well for his big tongue because the mouthpiece was broad (= large surface area on bars) but slim (=minimal bulk).
My horse Chomps the bit all the time, wether you're at home or a show. I've tried different bits /different saddle/ no contact (just standing in line with reins draped), doesn't make a difference. He's sound, not stressed and his teeth are great. I just belive some horses like to chomp on the bit. The only way i've gotten it to settle down is by letting him wear a fat snaffle in his stall for a few hrs each day.