My son Jonathan has been guiding the process of fitting the chain tensioners. The pulling chain, the part of the chain exercising force on the chainring, has to be kept straight – he said. You put a tensioner or pulley into that and the pulley will fall apart. That means I can’t use a pully on both sides of the chain to equal out the sideways force I need to exert so they miss each other.
So the horizontal chain has to remain untouched. But the chain diving toward the floor has to be pulled away. So it looks to me like the pulley has to go near the bottom of the picture.
Tomorrow I will cut the chain to length, turn it into one continuous piece and then drill through the frame of the bike – perhaps near the “204” marking – and fix the pulley.
This is not the configuration as the horizontal chain is being pulled down, but it gives the idea of what the pulley system will look like.