I don't use Putter Pal and The only equation I use is a simple one. Tourny speed using a putter with 15,30,60 scale.
Full meter ..15 goes 20ft, 30 goes 40ft, 60 goes 80 ft.
If you use avatar movements when putting -
30 scale - 3 avatar movements is 24ft.
60 scale - 3 avatar movements goes 48ft.
20ft putt up 4 elevation - 24ft. 3 Avatar movements on the 30 scale = 24ft. I would hit slightly more than 24ft to make sure it's not short
With all the other speeds I kinda guess using the same equation as above.
So on Champ green speed. 20ft putt up 4 elevation = 24 ft I would hit it about 19ft. Just short of full on the 15 ft scale.
I just go by feel and years playing the game. Not good at it but I go alright.
If I have putts more than 80ft I'm stuffed as I havn't worked out anything more than that lol. but rarely get into that situation anyway.