ATC placement help

Any ATC folks care to share how far they have their speakers from the back wall (from the back of the speakers, I mean)? I can do up to about 16" with my incoming SCM 40 v2s so I was thinking I'd start from there, but if 12" or something works better for anyone... They're big and heavy and we're seniors so the less fiddling the better. The same goes for toe in. I'm familiar with the sealed box deal and all the info I could devour online.
I just mean generally, not specific to a certain type of room. (Which will render any answers less meaningful, I know).
Thanks.
Marc