I've worked in the past a good deal with knitr and beamer for slides. One thing I'm noticing now with R Presentations that dynamic sizing of both the code box and the size of the code font seems to be missing. With knitr/beamer I could easily change font size with the size argument (e.g., size="footnote" worked for denser slides) as well as changing the code box width for my slides with options(width=...).
I'm struggling with how to do this in the current implementation of R Presentations - any suggestions?