This is most probably not fixed by only adjusting the front band. This comes usually from a lot of front band/clutch overlapp from the valve body.
Jack up the car on the rearend and have a friend accelerate slowly, then shift to 2nd, then keep accelerating (you stand on the SIDE and watch the rear wheels!) and then have him shift to 3rd gear and see how the rear tires will almost or even stop completly before 3rd gear comes! This is the harsh shift you feel.
1. get rid of this valve body and get a low band apply manual valve body! Just last month a friend his 727 blew up with such a no low band apply valve body and ALMOST killed him! Here are the pics he send me:
Index of /6o4o/spragfail
Next, get an orifice (from TF-2 kit) or even better, cut a 1/8NPT thread into the passage that feeds the front clutch. There you can install a plug with a hole in it (don't have my notes with me, but I thougth with a 0.14" hole to start with). For this you need to remove the valvebody. But as said, I would get rid of this VB anyway.
This will slow down the front clutch apply and decrease the overlapp you feel and see.
If the engine RPM's flare up, you need to increase the plug hole size, then the clutch engages to late. Just keep increasing till you got the perfect overlapp!
Michel