It is possible. I used the embed code for the presentation and added negative margins on the top and bottom. It took a bit of trial and error to get it perfect but once you have found the margin it works like a charm.
To be able to use this code without modification your Google presentation needs to be: 4:3 ratio (default is 16:9) - Go to File > Page Setup 1440x1124 on the embedded size in your Risevision presentation.
(This can of course be changed to anything matching the ratio but the margins would have to be adjusted to cut out the black, takes some trial and error)