Reach adjustment should never be done by adjusting the saddle.
Adjusting the saddle should be done to get into the right seating position for proper pedalling. Proper sizing of a frame should put the vast majority of people into a window where they can adjust the stem between say 80mm and 120mm - as well as giving some scope for personally prefference i.e slightly more streched out or relaxed.
Post layback requirements will be a function of the frame angles and lever length (ie leg bones) of the rider when setting up seat position.
While there aren't many older frames which cater for short leg long body types (horizontal TTs were the flavour for a while) there are plently of new frames available which have reasonable length top tubes and buckloads of standover. Modern Giants however have relatively little standover for the effective TT length so anyone with shorter legs would be best stearing away from these.
If you have a picture of yourself on your bike in a seated positon we will be better able to comment on the stem length and overall positioning etc on the bike.