There is a collar on our Corsair and Silverplate arches over which the base stack will sit. This collar has holes pre-drilled in it to accommodate folks who want to bolt down their base stack. We recommend using #10 stainless steel bolts to accomplish this. Bolting the base stack is not necessarily imperative if it is already supported by stack pipe that is going through the roof.
We also offer a Stainless Steel Base Stack option. Stainless Steel will outperform galvanized in terms of longevity. The benefit of the Galvanized would be a small cost savings up front.