Custom Length Exped SynMat UL 7

The Therm-a-Rest custom length thing has been done, and it works, but I don't own one of those!

I want to cut down my SynMat UL7 LW to 25"x40"

Is there anyone in the world wide web who has done this?

Is there any reason to suspect it may or may not work? And by which method of resealing....

The synmat is heatsealed. I believe that Exped uses ultrasonic welding, but a simple impulse heat sealer will still work, or even the venerable iron. The material will reseal at a new spot, otherwise it wouldn't have done it in the first place.