Not that it would be any safer, but you should be able to cut with a 3/4" bit at around 10-12,000 rpm. I use a 3/4" two flute indexable knife bit at work and I never spin it faster than 14K, even at 300ipm.
Not sure what you plan on cutting, but you might want to look into doing it in slices. And you can buy bit extenders to give you an extra inch or two. Or get a 6" long bit like these. http://www.vortextool.com/standard/p...fm?groupID=330
You might want to try this. Get a very long (5"+) straight bit and a very short one (less than 3") . Make a very fast, heavy cut with each. You should see a noticeable difference. Then imaging it 12" longer.