I know I am new and don't know as much as some of you guys but even I can tell you that is bull sh*t it wouldn't even do 50 of a cliff without a 70 kit on it.
speedos are set to show that your doing faster than you really are mind usualy around 4mph higher than what your actualy doing. so if your doing 30 your probs more likly doing 26.
Polini sport, i know of two that have failed, both on BW's interestingly...? Go for an Athena HP, im running one and its revvy and fairly torquey, about 7.5hp still running standard crank (until next year when it'll get an Athena HPC)