I don't know if this is useful information or not, but I can start my car in 3 gears out of 5. The lower gears will accelerate the car much faster. Just a suggestion that maybe gear 3 out of 8 is too low to pass the "no move" threshold.
I'm going to assume that you have started to work on the CAD already and have some crazy gearbox/shifter mechanism halfway done and are just trying to figure out the gear ratios. I'd really like to see how small and light you've made your 8 speed gearbox.
Wetzel