taking in the crotch is a horizontal movement. the thigh gets narrower but the rise stays the same length. dont let the alteration person fool you.
to shorten it must be done at the top. measure the distance from the waistband to the top of the side pocket.
its not a good idea to shorten more than that. because the pockets must then be moved down. and also the back pockets rise up too high.
a reminder, everyone should be sure when finishing the bottoms, to get the cut off cloth back. it just may come in handy.