My tailshaft has been shortened both ends, reversed, nuts and bolts mixed up and has never been balanced. Though I did have the welding done at professional driveline shop. I may be game but I'm not stupid.
Not an even a hint of vibration and runs true as an arrow. I know, I have a removable cover on my trans tunnel and have watched it spin under all sorts of rpms and loads.
Maybe I'm just lucky
BTW, psk, I like the idea of the falcon donuts, I must crawl under me mates xr6 for a looksee.