It works like this:
The first VUH is <pkg>/www/index.vuh and is the only user-accessible page in the www directory. This VUH performs all common processing (permissions/roles, common query vars, etc) and then does an internal redirect to an object collection-specific VUH (e.g. <pkg>/pages/collection1.vuh).
The second (collection-specific) VUH performs some processing and does an internal redirect to the real page tcl/adp pair (e.g. <pkg>/pages/<object1-op>) that then provides content to the user.
Are these internal redirects "heavy" operations? Do I incur additional page processing overhead by the RP for things like permissions checking? Compared to a normal tcl/adp page request, how much addition system processing overhead is incurred? 100%? 0%?