Has anyone ever used Phosul in place of SRF?

It's got 16% P as well as S. But I'm not sure about its availability.

Assume 100% water soluble. So immediate fast release. Usually insoluble %'s are mentioned for N-P-K. Strange as rock phos usually isnt that strong and usually says % unsoluble (with my ferts anyways) Probably processed in a way to get higher numbers and water soluble phos.

SRP takes like a super long ass time to begin to decompose. It’s something like a year or more before it’s fully available to root systems. Notice how the immediately “available” P is much less than the total amount of P; this is a good thing. A shit-ton of soluble P released all at once can upset the mycorrhizae. A steady release of minerals buffers ph for absorption. Wouldn’t worry too much; use this in the same way as adding SRP, silica, and/or gypsum. Not much different than adding all these amendments separately.