My Brooks B17 was causing pressure, discomfort, and occasional slight numbness in the perenium, despite raising my stem height, changing seat angle several times, adjusting seat height, trying different bars and stem... I decided to carve my own cut-out after searching the web and seeing that other people have successfully carved their leather saddles using just an exacto-knife.
At first I tried copying the cut-out shape that Brooks uses, but it wasn't a big enough cut for me. Then I just expanded it forward and made a larger oval type cut. This has been much more comfy for me, much less pressure. I did drill 4 holes on each side and used a boot lace to keep the bottom flap part of saddle together, which helps hold the shape. I've been riding it for a month or so now, with several 30ish mile days.
I'm definitely glad I did it. If you have a Brooks or other leather saddle that is almost comfortable, this might be worth a try before you give up on it or keep suffering. My sit bones still get a bit sore on longer rides, padded bike shorts help with that, but I usually go without them, and just wear jean or cotton shorts with boxer briefs.
And FYI, the saddle was not new, and had maybe 2 years of pretty regular riding on it. I'd call it broken in, but not super soft. I have a B-17 on my other bike that is much softer with about 10 years of use. Maybe I'll carve that one too if I start riding that bike more. Feel free to ask any questions.