I used to drive years ago (20+ )
I recently trained my 7 year old APHA/PtHA mare to drive. We have simple set up with an easy entry cart and now a bio-thane harness (sold my leather one for the bio one.) I trained her in an open bridle, mostly because I found the over check on the driving bridle too short for her naturally low head carriage. After getting a new harness (the bio-thane one) I am now using the driving bridle with blinder/blinkers and the over check (longest possible setting, leaving her at about level with her withers, which is more natural for her.) The lady I purchased the harness from included driving snaffle, which I didn't have before. I was using an egg butt with a leather chin strap to prevent twisting or having the bit pull through her mouth while driving.
Okay now for the questions!!
I see a majority of the drivers have mullen mouth, liverpool like bits. My mare doesn't approve of the mullen mouth (I tried a phase one myler and she hated it.) thus I use a snaffle. Here is the question (two parts): Do I need a bradoon with the snaffle for the check line? I have attached it directly to the snaffle right now. I have heard that the liverpool provides the "stop" needed that a driver doesn't have where as a rider may have undersaddle, this makes sense to me. Although she is very level headed, I did notice that she was "forward" when I was trail driving with a group a few weekends ago. I could see where having some curb action would help with control/stopping. She was by no means out of control, she was happy and forward. Is a jointed kimberwick like bit suitable for driving? Is there a reason that driving bits tend to be mullen mouths? I think that I could get suitable control without over bitting her in jointed bit with a curb. Is this proper driving equipment?