What do you need the flat patterns for?
At the last two places I have worked, we’ve done quite a bit of sheet metal design & the fabricators always seem to prefer to just get a normal drawing & work it all out from there.
They know their machines, so do all the set-up to get the right finished sizes.
I’d end up guessing most of the various sheet metal parameters & give them something they’d have to mess around with to get right, anyway.
Obviously, your requirements might be different or you might have more experience than me with sheet metal (not that difficult, to be honest) to get it all drawn up correctly. But, just thought it worth mentioning.