I just discovered this http://fswidgets.com...gmap_fs9_20.zip and I can't recommend it highly enough. I experienced no FPS hit, and the software seems to work flawlessly, in map mode at any rate (I tend to do VFR sight seeing, so I probably won't be using the chart capability; who knows though, this package may change my preferences).
I did have an initial problem which turned out to be a corrupted register following a previous re-install of FS9, but the solution was e-mailed to me less than 12 hours after I e-mailed the FSWidgets help desk. Brilliant!