I used to like the whole flatter rear end of the Turbo & Flite. The half-round section Concor and such felt like sitting along a log.
However, as I've got older and everything's gone a bit loose
I've got to like these:
WTB Rocket V, £30 or so...they have the nice solid flat bit for the sit bones, but have the groove and concave front/back profile to let the blood flow through your bits.
A bit like the Charge Spoon, it's not got much of a groove really, I think it's the concave shape that makes the difference.
I suppose the shape's a lot like a well used Brooks...but straight out of the box.
All the best,
Pause, take a breath and ask yourself: "What would Rastamouse