My preferred technique has always been to have heels off the floor- this has worked well for me in both rotary and fixed-wing. It gives good rudder control, and an easy and effective transition to braking when required.
I had a check with a guy who was adamant that heels should be on the floor until actually braking- he was barking at me (during the take off roll in a GA aircraft) to move my feet down the pedals until very little more than the tips of my toes were on the pedals. This was awkward and uncomfortable, so I didn't do it again.
By the way - what's different about the Aerocommander?
Cheerio!
CC