I took the Pressurized start button and split it into individual state files, and ran it through SKS's frame builder. It generated a start button that ran right (not backwards) but changed it from 86x30 per state to 455x40 per state, adding transparency. That's not a typo, it was 455 pixels wide per state for a total width of 6,370. I don't know what it's doing.
I'm patient, but not a total masochist. This is when I would stack the individual frames on top of each other in a single file, making sure to keep them aligned on top of each other. Resize the canvas width to [Frame width] x [number of frames]. Link frames 2 through [Last], scoot them the width of a state, unlink frame 2, scoot remaining the width of a state, unlink frame 3, scoot remaining, etc. until done.
A couple of things that I did notice while playing with this - it seems to me that while on the animation tab you have to apply the skin twice before any changes on that tab are applied. Also, as far as I can tell the "Delay between animation loops" setting is ignored. That might save you some trouble.