I'll agree that sit bone pain is normal until you break in your backside - but your description of excruciating pain after 20 min doesn't sound like normal sit bone soreness.....

It's been a while that I've been off the bike long enough, but what I remember is being on the saddle wasn't painful, what hurt was getting back on the day after or after a break - it would hurt for a few minutes and then that hurt would go away. Like breaking in a new pair of shoes.

btw - I have a several Jetts. One came on my race bike and I like it so much that I bought one for my rain bike - but everyone is a bit different, so what works for one person may not work for the next - keep trying. I think I'll go with the S works when these wear out - same shape, but thinner and lighter.