Old video but immediately came to my mind after reading this thread, here's Drew Doughty explaining his curve and why he switched to a toe curve many years back:
If you want to test the heel lift before making significant modifications, you could buy these:
https://www.thisissoul.com/products/superfeet-heel-lift
If you want to just do the heel lift, I would start with 1-1.5mm
That's really an old school mindset. The Kreps "p28" really isn't that big of a curve considering how widely used its is now. Brett burns for example uses a variant of the p28. A lot of players in europe use a kovalchuk or semin curve. I think its more of a factor of the european influence on the north american game.
The p28 comes from the player kamil kreps who used the number 28. You probably already know that.
I use a Kovalchuk/new Kovalchuk/Zherdev curve mixed that I had personally made. Lie 4