Leaking Thermostat Housing. Thinking on billet with O Ring

I too have had leaking stat housing issues. what worked for me was to drawfile the OE housing (assuming it ain't pitted severely) then cut a piece of gasket material from a sheet as tailor made gaskets are too thin (not referring to the thickness but they ain't wide enough to cover enough interface area between the two metal surfaces). & not overtorque the two bolts which can very slightly bow the housing, enough to cause a very slight leak.