Whats the fix for a seat "numb crotch" effect?

[JohnV]

The important part of the fit is height of the seat (among others). When you are at the bottom of a downstroke, your leg should be fully extended, unless you are doing BMX style riding. This, along with the angle of the leg (mentioned above) will make the bike fit you and help keep you from getting tired faster, unless you are totally out of shape. If you don't fully extend your leg when in the downstroke, you will feel it in the knees.

Quote:I'm considering to install a set back seat post to allow more leg room but this may put the crank ahead of my seating position.

If you do this, again, you want your leg to be fully extended when you are in the downstroke. In this case, you will want the saddle lower and more to the rear, such as the seat on a recumbent bike. Now your issue becomes handle bar reach and safe control.