If you get 2 soft pads, an extra $20 will go a long way in modding them.
$10 - 4'x8' sheet of particle board (found at Home Depot, Lowes, Menards, etc.) -- have 2 35"x38" cut from it (most stores will do at least 2 cuts for free, which is all you need to get the pieces you want)
$12 - 6 pack of 2'x2' interlocking anti-fatigue foam mats (Found at PepBoys -- other auto supply stores or alternately sports stores would likely have them, though maybe not as cheap). It should only take 3 pieces to cover one of the 35"x38" particle board sheets (pieced together, it should wind up 1 full piece, 2 half-ish strips, and 1 quarter-ish piece). The ones at PepBoys come with edge pieces, which means less cuts are needed to have straight edges all around. For an example of what these look like, see here:
http://www.greatmats.com/exercise.html
My process for attaching everything together is as follows:
- Tape down the foam mat to the particle board (using heavy duty clear packaging tape -- I've found it works well to tape in a tic-tac-toe board type pattern including the edges. When taping across, make sure to have a significant overlap that goes underneath the board.)
- Tape the DDR pad down to the combination foam + board. (use the same technique as for the mat -- ideally the mat should be flat, spread out as much as possible, and shouldn't move when you jump around on it)
Just the particle board alone I know has been mentioned by a lot of people modding pads, but I haven't seen too many mention using cheap anti-fatigue mats. I know it's definitely made a difference in the comfort level for me playing. It's probably pretty close to (maybe slightly better than) the high density foam that comes with the Ignition-style pads.