Tom,
I like the idea of the pumice pellets. I can't locate a store out here in the San Jose area that carries it. Guess next time I am in "horse country", I'll look for a Feed Store and try there. I am thinking of a 50/50% mix of the Perlite and pumice, as a starting point, to make up the "1" in the 3-2-1 Combo Mix.
I am also now experimenting with adding in 1 Cup of Epsom Salts along with the Dolomite Lime. I've now done this in 3 'Tainers for my second planting of Fall tomatoes.
Raybo