Thanks for the help guys

I have just bought an IV horse cavesson with bit rings
http://www.frogpool.com/tack/lungeing-and-training-aids/lunge-cavessons-and-lunge-reins/iv-horse-super-pro-leather-lunging-cavesson.html so could I use this with two sets of reins if required?
ros sorry so do you mean attatch the bit to the headcollar and ride from the headcollar or still from the bit? I'd be interested to know

We have tried putting the bit up a couple of holes and this has made her do it less but I kinda feel that's just covering up a problem by preventing her from doing it (in her case anyway). I looked at a couple of low ports but am concerned that her pallet is too flat and it could hit her in the roof of her mouth. Reading about mouth conformations of different breeds (obviously a generalisation) DWBs are known for big tongues and Trakehners for small mouths so not the best combination in terms of bitting

I think what I may do is get both of those bits to try out (which would only lose me a tenner if they don't help), then see if there is any improvement in either. If it miraculously stops her doing it, great (but probably unlikely!) if there's an improvement we're one step further on, if not we'll stick to what we've got and for whichever bit deemed most suitable maybe try your suggestions of putting a rein on the cavesson. I was thinking I could also wrap a jointed bit in latex bandage to lessen the flexibility but then again that would increase diameter which maybe counter-productive

I'll have a good look at her mouth this evening anyway.
