We're looking in to dimmer doubling at my church to expand our available channels on one of our FOH catwalks. We've got 4 year old Sensor3 racks with CEM3 (184.108.40.206.0.14) control modules. I've installed the dimmer doubler on a spare channel, changed the rack config firing mode for that channel to DD, and installed 77V lamps in 2 spare fixtures.
The problem is that when I bring up either the A or B channel by itself, I get flicker. When I bring the A channel up by itself, it performs as expected (no flicker), but the B channel flickers a low level. When I bring the B channel up by itself, it flickers itself; the A channel does not flicker in this case. When I bring both channels up together, I don't have the flicker. The flicker doesn't have any discernible pattern.
There is a separate issue that I don't know if affecting the dimmer doubling. For some reason, our design consultant spec'ed D20E modules for all 3 of our SR48 racks. However, the modules are set as D20 in the rack config. We haven't had any issues with this previously, so I don't know if it's a problem or not.
As for your D20E vs D20 question. The difference is the D20E is an enhanced module with a RiseTime of 500uS instead of 350uS with the D20 Modules. I just checked in Concert, and all the Default Settings for D20 are the same for D20E, so there should be no problems with using a D20E configured as a D20 Module. D20E may dim more quietly at the lamps regardless though of which Modules is set in the CEM3. Good that you got those modules. When the CEM3s get updated to v1.6.1, have them correct the module types with what is really in the rack, just to be correct though.