ignore if you have already done car-rig scenes before.
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car rigging takes time per setup, so budget for it.
camera size, weight matters.
know what shots you want and see if your rig can support.
plan for back up in case of bad/ disappointing weather.
get filters and etc for the shot (eg. polar for windscreen).
batteries. if you're monitoring the shot in the talent vehicle, find place to hide, figure out cabling. figure out triggering rec/stop or just roll and 'burn' tape.
lighting if required. interior rig or exterior rig.
figure out communications if shooting btwn cars.
Safety to your crew/ talent and people around you.
saw the rig @
http://www.dvtec.tv/id4.html
off hand, rig just looks a bit flaky. don't know if a ballhead or fluidhead can hold the shot 'steady'. inertia might be too strong for fluidhead to lock 100%. probably meant for low (10-30kmph)? speed shots/ gentle driving?
at the end it depends on how professional the result you require. if the talent car is going at a fast speed (>60), you may get a jerky-boat kinda image. add more shot variety to help your edit and as backup (wide shots, pans, etc.. 2-3++ sec stuff to cut away)