Here's a thought you might want to consider. Hospitals use an "extension" that sits on top of the existing commode. That could be a lot easier than putting stuff under it.

I ALSO HAVE THE SAME QUESTION. I WOULD LIKE TO RAISE MY EXSISTING STANDARD SIZED TOILET TO A HANDICAP HEIGHT OF 6". I HAVE A 4" CAST IRON PIPE AND NEED TO KNOW THE PLUMBING PARTS AND PROCEDURE TO USE CONNECTING ALL BY USING A 6" PLATFORM. THANKS!

better of just buying an ada toilet or you can get that 5 inch thick seat for around 50 bucks.

just my opinion i'm not trying to knock your idea.

Besides the seat (GREAT IDEA) get a handicapped toilet to get the extra height same roughin