Does this saddle make my butt look big?

I was talking to my friend, who is not horsey, about my saddle.

You know someone is a real friend when you can bore them with the details of your saddle and they will actually feign interest! Her hilarious blog is over here, by the way...

I was saying that my new saddle, which is a 15 instead of a 15.5 like my old one, fits now, but I'm currently in my skinny/fit stage. I gain one pound and its all over. The first place every excess ounce heads is my... hindquarters.

She was fascinated that saddles were sized to butts this way, and I proceeded to ramble on about how you can try to size your saddle based on height and weight, that there are charts you can use. I prefer the jeans size method since I figure that's a more accurate measure of my ...hind quarters. 'Cept for wranglers. I can't fit in any size wrangler, since have no waist.

But the problem with my hindquarters is that they are somewhat unstable, if you know what I mean. So I need the yoga pant equivalent in saddles -- elastic cantle and Cheyenne roll, some thing that can stretch to accommodate the occasional chips and salsa binge.

Maybe a woman really needs to have a fat saddle for that one week a month. Or that two month period where all food triples in calorie size. (mmm. egg nog...)

The new saddle (which currently fits my on the lite side butt and is perfect on Smokey's back) is a challenge in another way. I'm sitting in a completely different way. Many endurance saddles have this kind of seat, sort of flat on the horse. I always had barrel saddles which put you nice and deep. I'm getting the hang of it at the walk and trot.

The canter, notsomuch.

My big horn barrel saddle that I will never get rid of.
Fits Lily fine and most QHs... I don't use this saddle pad
with it. Must have been the only one handy...

My Tennessean that fit Cibolo perfectly
and may have fit Smokey. Sold during Rashid Clinic.
Cuz I'm smart that way.

So how about it, endurance riders? What's up with the flat seat anyway? Why is it better on long rides? There must be a reason - endurance riders are the least worried about show and all about go...