Jack's mix correction
I just finished mixing some more of Jack's mix and I found that I needed 4 bags of pumice instead of 3. I don't know if I made an error or OCFS changed the bag sizes.
1 Kellogg's Big R
1 Turf n Tee
4 bags of pumice
Mixed at 1:1:2, this produced 80 gallons or about 12 cu' or almost three large trashcans full of mix. That was at about $4 per cu.ft.
I have had very good luck with this mix and have used it for years. I first had 25% perlite but drop that for more pumice. Now it drains fast and stays just lightly moist, and does not seem to compact very much over time. It is a lot of work, but I like it.