You know, my 2 cents would also be that..................I've never found the grip on the G23/19 to be too long to conceal well, therefore I for one wouldn't have the need to do this.
But that's not what you asked. Someone will be along shortly to chime in or post a pic. I have seen this mod done, and I'd say there's really nothing wrong with it. The ones I've seen look just fine. And you do get the longer sight radius of a G19 with the short grip of a G26. As the poster above said, that difference might be negligible though.
It's an interesting concept though. A heck of alot cheaper than the whole "just go buy a G26" option, that's for sure.
Might check over on Glocktalk. I've seen a few of those over there that folks have posted.
I'll be interested to see your progress on the project, if you decide to do it.