@julsnet, I have 3 but I use 2. I'm not sure if three is allowed on test day. Id have them set to 12:00 for 35 mins sections and switch. On the third section id have to rewind. Then i'd reset them during the break. The writing section I wouldent time.
I've done the same thing and it made no difference... YMMV but I'm sure it won't be a big deal... Worst case scenario you have to ask for a hand grader or they just do it on their own because it gets messed up during the scan...