If you didnít realize it, thereís only roughly half of the amount of teeth on your cog engaging the chain at any given time. In the case of an 11 tooth cog, thatís only 5 or 6 teeth at any given time! Unless your thighs are as big around as a Surlyô carpenter pencil, you will be able to make any low-gear transmission required for general one-speed off-road riding skip AT WILL, using an 11 tooth cogÖ
Ö and its not so different for a 16 tooth cog, probably the smallest rear cog you might have on your one-speed ride. Considering that you donít shift, youíll be giving EIGHT teeth the full wrath of your wide load up the harshest vertical climbs you choose to attack. What my long-winded explanation is getting at is that more teeth are better when it comes to an off-road one-speed drivetrain. One tooth makes a huge difference out back with regards to preventing skippage. Wear life, too, is improved with more teeth. Since you never leave that gear, every mile you spin is on the same few teeth. Your drivetrain will last longer and will skip less and will launch the chain fewer times if you use larger cogs and chainrings.
I recommend that you pick a big cog out back (18 teeth or larger) and experiment to find a gear ratio you like by varying your chainring sizes up front. The weight penalty here is practically non-existent; there is no benefit whatsoever to using a "Micro-drive" drivetrain on your one-speed off-road bike. Donít do it! Itís dumb and youíre gonna hurt yourself on a steep climb.