i was at st ninians a few years back when the parade lap was started in pairs and 2 riders went under the bridge together and slightly touched each other sadly 1 of them riders came off as a result and lost his life
personaly i dont like the idea of starting in pairs
if you get 2 bikes/riders that are equal in performance they will be battling together on cold tyres round a few tricky bends and 1 might just try thet little too hard to get the break