I have the Turtle Top in 14mm - my mare goes okay in it but is fussy in the mouth in general (and always has been; she’s my homebred and I put a bit in her mouth as a yearling just so she could wear it and become accustomed to it - same at 2 and 3 - but she has always had a fussy mouth no matter what bit I try; it’s just who she is - and she’s extremely “oral” in general.)
Recently I lent my NS TT to a student, so have been using my Bevel bit without the ring leverage - it’s my jumping bit - and I put the reins on the main ring and sometimes on the leverage ring. The mouthpiece is a simple French link (not legal anymore, Oy!), but it’s thinner: 12 mm.
Ms Fuss has a VERY small mouth; thick tongue, low palate. She seems to be less fussy in the Bevel bit for flatwork, so I’m thinking that maybe I could try an NS with a thinner mouthpiece? Have been googling around and they seem to be available on Ebay - though not sure whether I trust the sellers. The major tack shops seem to only have the NS Verbindend in the thinner mouthpiece - but BTDT with her and though it worked well initially, she eventually started to hang on it. Go figure, since it’s supposed to help with that (mare is downhill and VERY long in the back and neck, short front legs so this is a regular challenge for her.)
Mary’s tack (which has a bit rental program - I have actually taken advantage of this in the past) has lots of NS loose ring bradoons but I didn’t see any with 12mm mouthpieces.
If anyone knows where I could find one of these unicorn bits I would very much appreciate it, TIA! 
