There is an API in RhoElements on WM called zoom: http://docs.rhomobile.com/rhoelements/zoom/, that's the equivalent of zooming in and out on the desktop browser (ctrl++ / ctrl+-). You just need to set the tag once and it will persist throughout your application. I'm not 100% sure what the viewport scale does, probably something a bit more clever.
Thanks so much for the quick reply. The Zoom API was interesting and good to know about but in my case didn't really do what I needed. It would ultimately still leave the over-sized screen objects but would only use a fraction of the screen to display them. After playing and Googling a bit more it seems like there are two approaches I can take. The initial-scale setting in Viewport actually works pretty well and from what I read seems like an appropriate use. An initial-scale of .75 sizes things pretty nicely on the 240x320 screen. Not sure yet if there are performance impacts (I suppose there kind of has to be, but not sure if they will be noticeable). The other approach might be to have a separate version of re_webkit.css for this screen size. In playing with the standard version, changing the form font size from 150% down to 100% seemed to get the sizing about right. There are lots of other sizing things that would still also need to be scaled down to really get it sorted. This would be more work but might be worth it if the first approach doesn't work out.
Thanks again for you ideas and help.