Not sure if the NC has the same size wheels as the ND, but I’ve done a swap from 205 to 215 on 17", albeit keeping a 45 profile. I would avoid going onto a 40 profile for road use, and Rainsport is a good tyre but they don’t last long and they’re squidgy in the sidewall; I went for an FK510 which seems sidewall soft too, other considerations were Goodyear F1 Asy 5 and Kumho PS71. My thoughts and all the maths are at New Tyres for ND - #51 by ckyliu
TLDR: speedo gets 1 mph more accurate and you have loads more grip.