When i initially had the consultation with the wow people, they said my horse could take no more than a 16.5 inch saddle.... and Im 5ft 10 / 11.
Initially they put me a 17inch seat on a 16.5 inch panels but I managed to lose a bit of weight (and had the flaps changed a squidge) so I could go down to the 16.5 inch seat.
The saddle my horse had come with which had been made to measure was 17.5 inch in length and had given him bruising over his kidneys
It bugs the hell out of me when saddlers only consider the height / weight of the rider when fitting the length of the saddle!
16.2 and 18" I would just like to point out though I am not a hefty fat bum, size 10 honest!!!! Only saddle we could get to fit his huge withers so I just had to go with it!!