In my experience unless you are trying to do away with the rear derailleur you may as well stick to a standard cassette at the back.
If you want to do away with a derailleur then something like the White Industries Double/Double crank and DOS ENO freewheel work a treat as really you only need 1 easy gear and 1 hard gear.
Alternatively to can run a close set of 3 rings up front and a single cog at the back with tensoner at the back for a dead simple 3 speed which works amazingly well.
If you want to do away with a derailleur then something like the White Industries Double/Double crank and DOS ENO freewheel work a treat as really you only need 1 easy gear and 1 hard gear.
Alternatively to can run a close set of 3 rings up front and a single cog at the back with tensoner at the back for a dead simple 3 speed which works amazingly well.