follow the above suggestions..
end up with a commonplace hat.
think about how you want the top to look
Knit straight up, and bind off in a X
OR knit some short row on top, and end up with a \ to the top of the hat.
or bind off in an I beam..
a half dome hat is fine... LOTS of people knit half domes.
but if you want your hat to be different (YOUR HAT) then one place you can make that happen is with the shaping of the crown.