Unless you had an oversized stand for your 29, the difference in length is 6", with the 29 gal being 30" long, and the 30 gal being 36".
I always like to have all edges of the tank on a good sturdy surface or it can create stress on the seams that you may not be able to see.
As Bharada suggested, a nice piece of plywood under will help, and it wouldn't hurt to put a couple of braces from the floor to the bottom of that piece of plywood as well to support the edges.
You'll really like the 30 compared to the 29. It's one of my favorite smaller tanks.
