Yeah they are great, both my bf and I have stupidly long legs. We both have 4 forward flaps, and have ordered 2 more with the same flap in barn. It just depends on how big you are looking for, every once in a while they pop up used.
Yup, another one with long legs here, 5'9, 135lbs with long femurs... I have a 17.5" 3L (long flap). Look for a "3L" for a long flap with an "equitation cut" to it if you don't have an insanely long femurs and don't like to ride really short, or a "3C" if you want a longer-than-standard flap with a forward cut. Their forward cut is very forward, I think more so than most people actually need.
4L/4C is a very long flap, I can't really imagine someone south of 6' needing one that long.
Is your height in your thigh or calf? This makes a HUGE difference. I am 6'0" and the forward(3C) flap way WAY TOO FORWARD for me and put my leg in a horrible position. I have the 3L and its perfect as even the flap on that is pretty forward as it is a jumping saddle.
"Using draw reins without spurs is like going to the bar with no underwear on. You're just waiting to get f***ed."
I had a rep out and she said I fit a 5 Forward flap, but because they *never* go that big, that she'd put me in a 4??? I ended up finding a used albion eventing saddle. I liked the CWD's though. I guess in your situation, you'll just have to ride in them first because they'll all be different. Good luck!