The platform you started with and the engine was a good engine but i wouldn't trust the way you put all the clutch and throttle since it is backwards :/ all the other gearedbikes I used I just took the derailleur off and used it like a single speed (old school...) it creates a cleaner look and less wires and then you don't have to worry about shifting plus also you can put all the throttle and clutch were it's supposed to be... And going 30mph on a bicycle it's best to go with what's the safest way possible... I've went 45 on a MB and it's about as scary as a 200lb fighting pit bull running after you lol so just be careful and don't do more than you think you can