Get the double. Who say's that if you have two bass pedals you have to use both of them? Get the double and practice evenly between single pedal(both right AND left foot) and double doing singles and doubles and triplets and especially paradiddles, holy h*** are those exercises useful. If you develop both feet at the same time doing the same exercises for each you will be very happy at how coordinated and strong your legs are...and don't forget to play both heel-up and heel-down, both are extremely useful and helpful for any drummer. Goodluck
