Re choice of gearbox, I tried box options and preferred the Mazda. Clearly this is very subjective, but I thought the gear change was much sweeter. On some tracks I guess the 6 speed option will be better, but I'm not fussed about ultimate lap times. On the road I think the Mazda option will be much nicer. So, for the mix of use i will have with the car I think the 5 speed makes most sense. I've left the engine / gearbox for now and will check with Derek on Monday. The gearbox is touching the heat shield on both sides and the bellhousing is just touching the heat shield in one place, but it is all clear of the chassis members. This is as good as I can get it and will double check with Caterham before I start connecting everything!