I was considering this as well, but not for increased width, but for increased compression. These stock seats are just too hard for my bum.
I bought some softer foam and just needed the courage to rip apart my seat to swap out the foam. Thanks for the thread sir.

I am going on 74 in a couple months. My thoughts on the stock seat are that is just about what a 2x4 would feel like. I bought a Sargent seat right after I got the 09 klx250 last summer. It is wonderful. If I had one to copy I think I would have copy ed one. One bad deal with the stock seat is that the top tends go go right up the crack in your butt making every thing back there sore along with my back.
As far as I am concerned it is the best mod money can buy, more power is nice but if you hurt to ride it what good is it?

Yeah stock seat part# B-U-T F-L-O-S-S

Excellent. It never occurred to me to sew panels on the side to accommodate a wider seating surface. I can see this in my future.

Did you adjust the seat base or only the foam?//

Didn't do anything to the seat base. Just glued foam to each side of the existing foam.

Side note: Interesting that Photosucket didn't delete my photos, but another photo in this thread was deleted. :(

Hm, And I went the complete opposite way. I shaved 1 1/2" off of my seat. Give me a 2x4 for a seat and I'm happy......LOL The more time you spend riding, the more you get use to the seat. Look how small the road bicycle seats are. Some guys wear padded cycling shorts which really work great on dirt bikes. Maybe another option some of you can give a try. I wore them years ago. Big difference, nice and cushy for your tuchy....:D

I have bought an old KLR 650 seat which is slightly bigger. I have adjust the base to fit my KLX 250. I am about to add some fiberglass to the seat base to make it slightly wider. then do as you did with the foam, Apart from adding some different density foam and some seat pad gel. I want a super comfy seat for touring Indonesia next year. So i want to keep my old seat for when i am finished my 3000km tour. I am finding it difficult to get any decent seat cover material here. But i will find something.. Cheers
George