After MANY versions I finally made linkage that works to control all four sets of points with a single Tortoise. The solution was to use a stiff push/pull rod connected directly to the Tortoise drive. I used a piece of NS rail with copper plated "wire feed welding wire" for the connections. Two wires at each end connect to bell cranks with a wire going up to the switch bar. Having both bell cranks movine the same direction the rod moves back and forth rather than having a "reversing" crank like one early version. One note of caution. Since the wire coing up to the points does not pivot like using a Tortoise per switch bar it moves further to the sides. The holes need to be larger or at least "cone" shaped to accomadate the outward bend of the control wire. Why bother? My layout has 4 Double crossovers. If I only had one it would have been easier to just use 4 switch machines. 4 versus 16 saving 12 made it worth the effort.