I just used some spray high-tack to hold the gasket into the housing - I hate being anal but the dumb thing should fit the machined part of the housing . The issue here is if you went to any other material you risk changing the durometer of the rubber and not allow it to seat the base housing gasket . Seems to work fine , no hot coolant in the upper hose until the thermostat opens so I think so far all is good . Engine does seem to run better so far but it's been nearly 40* here , odd weather for our state in January . I use liberal amounts of sil-glyde on the gaskets to prevent them sticking and getting pulled out of alignment , sure makes it nice working on stuff years down the road too .
Sarge