Hi all, first post on this site. Question is I have a 1mtr roller gun with 7mm 140cm shaft and thinking of going to a heavier 7.5 mm shaft same length, I have been running 14mm and 16mm rubbers cut to 50 cm with full pretension. If I go to a 7.5mm shaft (for penetration at distance) do you think 16mm rubber will throw the spear hard enough or should I go with 18mm rubber? I use a load assist so loading is not a problem. Thanks in advance.