I have to laugh a bit at all the comments about how difficult it would be to make single-length clubs properly, when not only Pinhawk--with which I have only recently become familiar--but especially David Lake with his 1 Iron Golf set has been successfully building and selling these for at least a decade. 1 Iron Golf was mentioned early in this thread but I didn't see any other comment about it.
Lake basically maintains there isn't any good play-improvement reason for the variation in length of most clubs. The different lengths within groups have very little effect on distance but they do help make you less accurate. Win-win! Not!
I've played his clubs for years and love them, and far more accomplished golfers than me use them. The irons are one length, the woods are a different length, and the driver is yet another length. He recently came out with a newer "pro" line that I assume are more accurate and less forgiving.