Wanted: Old beaten track cog for rat bike

Would only work with splined sprockets really as you can't guarantee where the sprocket is going to stop. It might end up bang on or it might end up half a tooth out. With a freewheel you'd have to get a decent quality one with high tpi to make sure the stress was taken up by both sprockets.

We did this with a bmx and a double fixed hub years ago, you can get bmx freewheels called southpaws which go the wrong way as well (intended for left side drive).