Finding the right girth length

Hello!

I want to order a new girth for my Barefoot bareback pad (while the Cdn $ is stronger than the US), but I don't know what size to get. I've been to a couple of sites that give a bit of information on calculating girth lengths. One says to measure the heart girth length, divide that number by two, then subtract three (and round up to the nearest size). On a horse that measures 79 inches around the girth, that means you have to order a 38-inch saddle girth! The one we have on the saddle is 27 inches, I believe, and that's too long!!

Another site says to put the saddle on the horse, then measure about half-way up the billet.

I also recall reading somewhere (maybe in a treeless saddle group) that the girth buckles should go no higher than the horse's elbow, otherwise it contributes to slippage. Having your girth too short can also cause problems.

When I have Fanny saddled, the buckles are pretty much at mid-point on her barrel, or maybe a bit higher, as her barrel starts to narrow towards her spine...and we have slippage problems.

The bareback pad has those wonderful sheepskin pads that I'm assuming should be somewhere along the horse's sides, but with the girth I have now they are crammed up against the bareback pad because the girth has to be done up so high. Even that way the bareback pad probably isn't tight enough and I should remove the sheepskin pads in order to achieve that.

My husband and I once tried to do a measurement that was about even with Fanny's elbows, and that was only about 22 inches! I thought I'd be generous and order a 24-inch girth, which is still shorter than the girth that I bought with the saddle.

Help!!