Best way to split main file and SI, with cross-references

[fxcoudert]

I have now written and published more than 50 papers (and probably close to 100) using the achemso class, as I have been using it for years for all my LaTeX papers (ACS or not). So first, I want to thank you for your work on writing and maintaining this!

One consistent pain point in my group has been in how we deal with SI, and references from the main text to the SI. In some papers we do it manually, in some we have set up a system of macros and latexmkrc rules for compiling in the right order. But it's often fragile, and generates frustration or weird warnings (or both).

Is there a recommended way to do that? If not, could it be added and integrated into the "demo" project? That would make the package a lot more ready-to-use. (I'm not sure what the contribution model for this is, but I'd be happy to try and help, though my LaTeX skills are limited.)

[lzhzzzzwill]

u r true hero, let's do it