The CSR spoilers (and front fenders) are supposed to help quite bit.
There is a Caterham in the UK with 300hp that has been 159mph (with a quaife sequential 6-speed)
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And as you know, there is a guy on the 7's forum with an WMC Ultralite S2K (7 like replica) with nearly 400hp that supposedly did 176mph in his, but he has all kinds of wings all over it to keep it on the ground and the body style is slightly different