The adjustable stock option seems to vary a bit on where or when you buy your 715T.
I had a non adjustable stock.
few seconds with a dremal and a key ring and instant adjustable stock.
the post in the stock is spring loaded. Everything else is there to make it function except for the tab hooked to the pin for adjustment that is found on adjustable stocks. Looked all over for this part with no luck. So I will either make my own and drive a cold rolled pin in or leave the key ring in.
made a small half moon cut on either side of the pin, 1/8" wide and almost 1/8" deep. push down with a safety pin next to the pin and catch the hole in the pin that would normally have the cold rolled pin in it. Pull it up and move the stock half a hole legnth to keep it exposed. Remove the safety pin and insert a small key ring into pin.
instant adjustable stock for the cost of a key ring and 5 minutes of your time.
naturally a pic is here to explain things. This is a pic of the pin in the up position between holes so you can put the ring into it. and you can see the half moon slots i made on the sides.
hope this helps
Dave