According to the Help & Manual documentation their is only one argument for specifying skin files, ‘O=[skin]’, which we’re using when you specify a skin in the action. Have you tried to see whether selecting a skin works for Browser Based help projects? If it does, I’ll remove the ‘CHM only’ text in the action properties.
you are right that specifying the /O switch to H&M is used to specify the skin also when building Browser Based Help. However I have the impression that FB does not pass the /O switch to H&M when building Browser Based Help, as I did specify the skin in FB but I got non-skinned help instead.