[asid61]

For your drive purposes, I highly recommend that you just design a 4 cim gearbox. Or, better yet, decrease to 3 cims.
Also, instead of using gears to combine the motor output, I would take a look at 192's design which uses belts for the first stage of transmission. You can combine the outputs of all the cims for a lot less weight that way instead of using gears. Then just use the shifting stage to shift between a 14:40 and a 34:60 stage (both of those shifting gears are sold by WCP) to get the last transmission stage.