OK - I was just being a dork!
I tried it again, and inserted the plugin *before* my amp sim (S-Gear), and it works fine.
It sounds nice - not "overblown" at all ;-)
NOTE: It certainly seemed unhappy running after the speaker emulator
(S-Gear -> Torpedo WOS 4)
Maybe the level was too high, or maybe it was annoyed because I had it set for mono (the guitar part is mono until it comes out of S-Gear, and then it is stereo) but it's working fine now ;-)