I’ve seen it done. While your at it, it’s also a good idea to run a wire from the roller pickups on the trailing unit to the solder lug on the e-unit in the lead engine. If you’re running three wires between engines you may as well run four and improve the performance. I especially recommend this if you are connecting MPC-era engines together.
As far as overload on the contact points on the e-unit, if you try to daisy-chain dual motored engines together the amperage could become too much for the contacts to handle. E-unit drums will heat up and melt on occasion.
