[MacRuby-devel] How do I install bundler without disrupting my MRI bundler

If I try to install bundler using "sudo macgem install bundler", it wants to over-write my existing bundler that is located at usr/bin/bundle. This is obviously a problem because it breaks bundler for all of my MRI projects. So I installed rvm, thinking that it would keep the gems separate from each other, but when I switch to macruby with rvm, "gem install bundler" doesn't install it with the macgems, and so bundler isn't accessible by macrake. Any ideas?