wiley: the one-way is locked and unlocked via that nut on the main layshaft. When its cranked all the way down and tight agaist the two pulleys, then the one way should be locked. You can check this by holding the spur gear and tugging the front belt. Not too hard! Just make sure that one pulley wont move without the other. To unlock it, loosen the not and give the two pulleys a slight pull in opposite directions to free them from each other. This will leave you with full one-way action. Of course you can go anywhere between full lock and full unlock. MikeR and most others here use the fornt one-way also. I don't use the one-way enough to go for the $60+ front one-way, but maybe I will one day.
Also if you have indeed read all the post here on this thread, you have seen the tips on how to make sure the one-way pulley doesn't slip, so I would suggest you pick one of those methods(either with the glue method or set screw method) before you do too much one-way activated racing.