The photoshop plugin only works on a Windows machine - it would be really cool if we could just copy the .8be between systems but it isn't as simple as that. One potential time saver is to run the command line version of the plugin - hdmake. If your doing a lot of conversions it might be easier to script this, and I'm pretty certain that this would run just fine under Parallels.
Just to be clear in the plugin you need to select either 'Dual' (the default) or 'Silverlight Deep Zoom' to produce cross-platform output. You don't need to export twice (I'm not sure, but I just wanted to make sure that you weren't suggesting this when you said "export for both"). We currently don't provide a way to transcoding from the old HDView format to the HDViewSL format. This would be a nice feature to add to hdmake, but I'm not sure when we'll get to that. Note that the only time you should need to select 'HD View' only is (1) you want to distribute 16bit or 32bit imagery, (2) you want wide-gamut colors, (3) you reall care about the 60% smaller output size.
I'm sorry that I couldn't provide much help here.
-Matt
