yes. id use a non metal bung as its lighter and as a result puts less strain on the redundant hose. something nylon with a rib so the hose clamp has a good area to clamp. an alloy blank knocked up on a lathe would be ok though.

the s1 t3 is effectively oil cooled rather than the s2 having oil AND water cooling. the water coolant is heated by the turbo rather than the coolant cooling the turbo/engine. best bet imo is an oil cooler if temps are on the hot side of ideal.