Yes Sarahlouise you are correct with the two attractions you mentioned. The single rider line for parachute drop moves very quickly and I have rarely queued for more than ten minutes there and this is probably due to the seats holding only three riders. RC racer is a different matter and you can sometimes wait longer in the single rider line than the standard queue as this attraction seats four abreast.
They did experiment with a single rider line for Crush, but this did'nt last long and was considered unworkable by the resort.
I believe that there will be a single rider line for the new Ratatouille attraction when that opens in July.