Federico,
Velocity isn't really the issue as you can just increase your ignition cut times, but at that point you are slowing your shifts and the whole point of the system is lost. What engine are you using? If you've done your gearing appropriately and have a reasonable power spread then it's likely that on a typical FSAE track you will only use 2-3 gears. Personally I don't get why people bother with complicated shifter systems when a simple hand actuated stick does the job with much less headache.