Originally posted by Julius
In very tight twisty tracks an overdrive might be helpfull. We'll see if a 21 pulley is a worthwile option.
There are no plans yet so no need to ask for release dates 
Thanks for the little bits...
A slight front overdrive in the drive can also be achieved by using the 705's 46T rear diff pulley instead of the 45T. You need to do some things to make it work though. That'll be worth about 2.5 mm of tire split.
Or you could use the 23T pulley and the necessary aluminum pulley adapter (also from the Impact / 835 / 705) to get overdrive in the drivetrain. Using this would make for about 3.5 mm of tire split.