i recently received the 2x kit from ulticreatr and mounted it to my ultimaker 2+. They didn't shipped the firmware with the kit, so i just branched the original ultimaker2marlin and patched it for the dual extruders.
Moreover I patched the power consumption problems of the ulticreatr2x kit in a very naive way.
The problem with the power consumption is, that the original power supply is not strong enought to serve the 2 heaters, each with 2 heat capsules, and the heat bed at the same time. It is only possible to switch both hotends on or the heat bed, not even one hotend with the heat bed is stable.
I solved it by a simple bidding approch, if one of the hot ends is requesting power and the sum of both hot end requests is greater than the request of the heat bed or one of the hot ends is requesting full power, then the hot ends are served. Otherwise if the heat bed is requesting power it is served if it is requesting power.
You can find my changes in my repo on github, feel free to use it or to improve it
One thing i have in mind, is to average the power consumption, e.g. start the heat bed after at hot ends are switched off within a pwm period. it is as well very easy, but currently the first approch is working fine, so no need to change