Join Date: Feb 2012
Location: South Wales, UK
• Horses: 0
Interesting question.There are usually two issues with long-legged riders - femur length (most common problem) and lower leg (less common but more difficult to deal with).
As far as the first goes, I look at it this way. In theory, if you sit in the saddle without stirrups so you're balanced in the middle (low point) of the seat then move your legs into jumping position, your knees move forward and up. You don't shuffle your seat backwards, or you shouldn't, because then you'd be sitting behind the horse's centre of balance. That means flap angle is the most important consideration. In practice of course you tend to naturally move your bum back very slightly, so seat length IS a consideration, though it's secondary.
Stirrup bar position will make a slight difference as manufacturers tend to fit them in an 'average' position, but from that point of view they are governed by both the tree shape (they're attached to the point and the rail, so angle of the point makes the biggest difference, and we don't want the point at too forward an angle as that drastically affects fit behind the horse's shoulder) and the bar castings they have available.
Lower leg length affects what length of flap is comfortable, usually because the flap catches the top of your long boot which is really annoying. It's more difficult to sort out simply because few manufacturers offer shortened or extended flap lengths.
I've found the majority of cases where riders leg moves forward over the front of the flap are due to the saddle not sitting in balance on the horse with rider mounted. It's a particular problem with croup-high horses, especially those with flat withers. Saddles designed for this type tend to have flatter trees so they sit lower in front. When the rider mounts he/she tends to rebalance by sitting slightly back from the vertical, and as the saddle doesn't sit level with the ground the flap edge is behind it's usual perpendicular so the rider's legs sit apparently further forward than they would on a correctly balanced saddle.
Sorry for the long post :)