Saddles not supporting the sit bones - what to try next?

[BleeckerSt_Girl]

Try a B17 first- it's sort of a woman's size 'middle of the road'. Few women are too narrow for the B17. If the B17 is too narrow, try the widest Brooks- the B68. I don't recommend you start with a Swallow or Swift unless you are very narrow boned. I also recommend you get the regular B17 to try first, not the B17S, which has super short rails and really limits your fore-aft adjustability.

the tall sides look uncomfortable even on the B-17 narrow. Also the cutouts on the Imperial versions look very rough, like they would pinch

You can't tell anything by looking at them. You're just used to looking at racey styled plastic saddles. And when you get a chance to examine the Brooks in person, then you'll say "Oh those are sooo hard!- they'll be terribly uncomfortable!".
You have to ride them. Your butt does not have eyes. lol!

[Biciclista]

The cut out of the imperial does not pinch. Now I've never ridden it NAKED so I don't know how it would perform in that condition. But the chances of that happening are pretty small. With clothing on, jeans or padded bike shorts, i have not detected any pinching, just a subtle LACK of stress in the area it was designed to protect.