More sit bone questions

Wasn't sure the best place to put this - so I thought I'd go w/ the area where happy & well seated tushies rest.

If you've found the sweet spot where you can sit on a saddle & have your sit bones appropriately supported, how much additional clearance do you have from your sit bone out to the edge of the saddle? (Imagine sitting on a ruler that goes straight across both sit bones.) Is it mere mms? or are we talking cms + of room?

I'm trying to decide how wide of a saddle I really need for sit bones estimated at 150 wide. I'd also email brooks directly, but their contact us web page is down.