I converted the stock HI Beams to HIDs in my Freemont. I use a driving light relay harness to power the modules and the stock harness to provide the signal to the relay. Results are that the HID's flash once when firing up and then build up steadily with no flickering.
The road laws in OZ states that "using HID's in the main beam (dipped, or low) the headlights must have self leveling and washers. In the HI beam (driving) there are no restrictions as you should dip your light in oncoming traffic.
That's why hi beams only, low beams require all the extra's to stay legal, not to mention as above the low beams setups are very specific to the light globes fitted and the optics of the reflectors are not set up for HID's.