Hi, I'm having the same issues you had about sinking forward into the seat towards the tank, just wanted to ask how the seat is still performing?, Baldock is not too far away from me and what you have done seems like the solution I also need
I too suffered from the crushed nuts syndrome - worse with the low seat option but still there with the high seat. In an effort to keep the front of the seat raised whist keeping the rear low I took a hacksaw to the plastic spacer collar used in the high seat configuration. I shaved off the spacer blocks at the rear which lowered it sufficiently so that the front was high but low enough at the rear to fit the front pillion plastic spacer. That worked and I've done thousands of comfortable miles since. I didn't have a problem with seat comfort apart from that so didn't need extra padding, so if that is you then it's worth a try. If you cock it up and ruin the plastic spacer surround they only cost about £10 a side to replace.
Here you can see how the seat looks on the bike. There's a larger gap than normal between the seat front and tank which could be filled with some black foam or piping, but it's been like that for a while and it doesn't bother me. My hacksaw work was a bit crude and no doubt a neater job could be done. But as it is under the seat and out of sight I'm OK with that. The front 'high' bar is fitted and the sawn off spacer blocks at the rear allow the seat to be lower there and the pillion seat filler strip fits well. If you wanted the seat a tad lower you could remove the rubber pads on the top tube frame but I was happy with the height so left them in situ.
Yes, could be neater with a little bit of black foam/rubber strip. I Initially intended to do that but, being a pragmatist who values function over form, as time wore on I appreciated what it was - a more comfortable seat. It's not really much worse than standard, as I purposely highlighted the gaps with the photos to show how it looked. The real problem is that Ducati didn't make it ergonomically comfortable from the off.
