Most DD'ers would be able to have DB killers (I think everyone racing last year took them to Assen last year for the Friday) tho its doubtful that not all would have full tachos fitted! (we dont on one of ours, just limiter lights).
Then again, anyone doing trackdays at ANY MSV circuit is limited to 105 anyway, so will be taking precautions to keep within this, surely?
Its not rocket science tho, and cheap rev counters are usually available to purchase on ebay etc. As long as the tester knows its a twin, and does it at 50% of the rev range, and the usual required distance away, there isnt usually a problem
