I really like my Hinterberg stretch frame. It can take the weight of my Voyager 17 (an old, heavy, industrial stretched Singer), which many frames (including the Grace frame) do not handle well. You can start with this frame and a standard sewing machine (takes some tinkering to figure out how to use it) and not have to change the frame later when you buy a larger throat machine. See
http://www.hinterberg.com for more info. Sometimes you can find the Hinty stretch frame used on Craigslist.
Edit: If you really want to make your own frame, several on the QB have successfully used the Ken Lund frame kit. Do a search on the board for Ken Lund to find posts about it. Here is a link to one:
http://www.quiltingboard.com/main-f1...e-t195959.html
He has a lot of Youtube videos about quilting with his frame. Here is one:
http://www.youtube.com/watch?v=F24UUQdBW5I
and I think his blog site where you can purchase a kit is mentioned in the video.