Hard to say. When I had a mazda3, I originally had a TWM short shifter, which primarily shortened the shaft. I really liked it, until I got a chance to try out the Mazdaspeed STS, which only shortened the shaft a little, but worked mostly with the cable attachment points to shorten the throw.... I much preferred the MS part, but both were better than stock IMO.
I wouldn't spend a whole lot of time on it, but if you have the welder and you have the spare shifter, I don't see any reason not to at least give it a try.
For what it's worth, these opinions are coming from someone who also gets a good deal of satisfaction from tinkering and DIY work.