Hi guys from a newbie contributor but old hand club racer. I would agree about the cost of wringing the last critical fraction of power from a small street motor and wonder just how long a small four stroke would last given the flat out nature of the course. Any variety would be interesting at the TT. Small bikes may be fun to ride but how about, in the future, looking at some of the new triples from triumph and yamaha with relaxed rules on chassis and a new capacity class. In a few years there may be some more interesting supercharged motors or similar if manufacturers are not beholden to 600cc markets. Maybe in many, many, many years there could be an electric bike race. . . . .