How to replicate SGP stretch manually?

Hi all! I’ve been using SGP for a few years now but my activity has picked up recently ever since I upgraded my camera (used to have an SBIG ST8XME, now using STF-8300). My question is this - I really like the way SGP auto stretches images but am having trouble replicating the auto stretch results in post processing. Can anyone explain how SGP auto stretches in a way that can be done manually in another tool?