I built two, but with the green coloured 20mm driver, see this thread there is also a video of the UI of that 'first gen. green coloured' intl-outdoor 20mm mcecolour driver. About adding 7135 chips: in that driver at least there is only one 'entrance' of the circuitry from the minus for all four dies, it is a tiny component that already gets red hot from the max 800mA that the driver draws. That may also be the reason that at any given moment just one of the four dies lights. They apparantly redesigned the driver and now there is also the blue version, in 20 and 17mm. I haven't looked at those closely enough but at least by combining the stars there are options that two dies light at the same time.