Putting the Extron interface output through an UMSA would be safe since that would (or at least should!) correct the signal down to SCART spec levels, but people have been criticising ArcadeForge’s customer support lately which is a shame as they make some useful hardware.
I think I’m going to try this solution. Hopefully Arcade Forge has solved their issues by now. Should I be careful with the interface-to-UMSA cable, or any BNC-VGA15 will do? (I’m thinking about the input/output direction options you can find in RGC solution.)