moving the seat to compensate for poor fit of the stem of the top tube is a temporary fix at best. If the bike is fitted correctly the position of the saddle in relation to the knees and pedals is very important.

The only reason I can see to move the seat is just to get the feel of what the correct lenght would feel like when the cockpit is adjusted correctly. You don't want to leave it like that tho.

WhenI was still riding my Giant HT, the cock pit was way long and I could never truly get behind my seat for down hills and steeps. A buddy of mine did a field adjustment of moving the seat FORWARD just so I could understand what the cockpit of a mountain bike might feel like whne it was shorter.

Irulan