a dyno day would consist of just one day…say from 11am to 5pm or something along those lines (just making a example) and a cheaper rate per person for 2 or 3 pulls (like $75 per person). Just a time for power pulls.
honestly, the amount of people that would be interested would depend on the cost of the pulls. A local shop did a dyno day last year and it turned out ok…synapse did one two years ago and it was a huge event. Atleast 10 cars on the dyno with pizza and drinks and what not.