Will it work?
Negative Ghost Rider the pattern is different...
However I did read of a guy the did do it, but the slide hung off the back side, not sure what he did about the different locking lug geometry!
It wont work. I have tried it before and the barrel lugs geometry are just different enough where they just wont work. Probably would have better luck cutting down the frame of the 20 to the grip length of the 29. if you are looking for that option. Some gunsmiths offer this service.
Not only will it not work, but if you try you can get things tied up in a way that you have to disassemble the slide while on the frame to get it back off. Ask me how I know :(