I find the same issue on my Z400 - pushing my 'nads into the tank.It’s not the comfort per se. It’s just that it’s difficult to meep myself off the tank. Riding a road bicycle, I’m used to hard uncomfortable seats. Would a different seat push me forward the way this one does?
I bought the kawasaki Z900 upgrade seat to raise it up a bit plus make it more level and soft. Well worth it. I presume the same will apply to the Z400 (I might invest, as the Z400 will become a long range commuter soon). Unfortunately the Z900 and Z400 seats are NOT interchangeable.
Unless leg length - height is an issue - the Kawasaki Z400 upgrade seat - if one exists and follows the Z900 pattern, would solve a lot of issues.