Those plastic cup thingies are the wrong dia & wont work, I super glue(or something similar) to hold the side gaskets in place & I always use some gasket cement on both sides of the port openings(SPARINGLY) whether it calls for it or not . As said you want those horseshoe openings left open if you have a functioning heat riser(I dont like it functioning) , too much heat & affects the volatility of todays fuels. If not functioning you could cover it if you so desire(they do look ugly)