Rear Seat Questions

[elks]

Ok I have a seat out of a 86 Blazer getting ready to go in. To keep from cutting up the original bed I have created a frame out of 2" square tubing. Well I was messing with it and could not decide where to put the seat. I like the storage area in the back, but how far back should I go? There will be the occasional coyote hunting buddy in back, but the vast majority of the occupants will be my 3 yr. old daughter and my 3 month old son.

Any pic and measurements would be great.