I don't think display speed will be a problem. Electricity moves fast! And you are only switching 20mA. If you read the datasheet, time is not mentioned anywhere. The 100's will be a blur, you may be able to make out the tenth' as they change at 10 times a second.
Display speed wont be a problem.. when I said "they need to be read at fast speeds" I was referring to the digit size as they will be in pause mode when being read by the rider/driver.
What have you ended up with for a power source?
I haven't sourced one yet.. I am going to use a power drill battery like you suggested before until I can find a good one. I want something slim so I can place it in the middle of the unit and try to keep everything balanced. 
I am going to download your zip now and report back shortly.