Hello, MattG.
Yes, you can use 1 SSO and 1 Web Client service to get "single-pane-of-view" for 2 vCenters, i did the same thing recently, and you don`t need linked mode. Just point to your SSO and Web during installation of both vCenters. But in this case you can manage both of them from single point only in Web Client, not from thick vSphere client. If you need to manage both of them from single thick client also, then you should make linked mode, but in this case as far as I know you should also install multi-site SSO, not simple SSO node. I use the first scheme.
Sorry for my bad english.