I managed to get the viewports showing in Hammer, but then I ran into two other problems.

First is if I change the SteamAppID in gameinfo.txt to 218, the Orange Box engine, then the viewports are good, models are showing, but the mod won't run.

But if I leave the SteamAppID to the default 420, the 2009 engine, and change the ToolsAppId to 218, then the viewports are good, but the viewmodels (info_player_start in the editor) are erroring.

Does anybody have any solution to this, or the 2007 SDK plain simply doesn't want to cooperate with me?