In regards to the french link bit and the copper/moisture thing....do you think having just the center link in copper to be sufficent enough? Also, what is the proper way of measuring for a bit?
Well...there is nothing that says that you have to use any copper, it just seems to help the mouth salivate, and that would be totally dependent on each individual horse. Bitting is such an individual thing. I have a couple bits with a copper link and they perform differently on each horse. I have one horse that there just isn't any "slime" no matter what bit you use, and others that just look at a bit and will slobber all over you!
I have also had top trainers that don't think that a moist mouth has anything to do with the quality of the performance. So I look at the form and fit of the bit over whether or not it has any copper. If it happens to have copper on it, fine.
As far as measuring, the easiest way is to get a wooden ruler (without a metal edge) and hold the ruler at an increment, like 1" or 2", on one side of the horse's mouth. Then place your finger at the other side of the mouth. Without moving your fingers, slip the ruler out of the front of the mouth and read the measurement. Be sure to calculate for the increment you were holding the ruler at. So if the measurement is 5 1/4", deduct the 1" where you were holding the ruler and you have a 4.25" mouth. Be sure not to "squeeze" the mouth as you measure. I like to barely touch the lips of the horse. Fatter lipped horses are going to take a wider bit than thin lipped horses.
The absolute easiest way to measure a horse's mouth, especially a mini horse, is to get a BitFit device.
http://www.theoriginalbitfit.com/ What I like about the BitFit is that it measures the cheeks of the minis as well, because some mini's cheeks tend to widen quickly above the mouth. If you only measure the mouth and parts of the bit bump the cheeks of the horse even though the mouthpiece fits, you will still have an irritated horse.
As far as measuring the bits themselves, I don't always trust what is on the tag. If I purchase a bit, I like to measure it myself. The mouthpiece measurement is taken between the "cheeks" or rings (or sometimes "purchase") of the bit. It is important to measure from inside to inside, not outside to outside. Again, the more bit that is above the mouthpiece, the wider you may have to get. Some people will even try to bend the purchase out a little. Obviously, this is not possible with a snaffle.
Myrna