Andy, The only comment I would add is that the HANS is an additional safety device and is nor solely restricted to use in classes 5 and above, you will find plenty of competitors in classes 1-4 that have voluntarily opted for such a device. There may be no need to have the harmess mounting points adjusted but you won't know until you try a HANS device, maybe there is another competitor near you who can offer assistance, we're a pretty friendly bunch There was a 420R in class 4 last year running on, I believe, ZZS tyres. The clubs regs often change as a result of accommodating the changes in Motorsport UK regs. My car has been in classes 4,5 and 6 over the last few years, but has been running the exact same spec including tyres. Whatever you decide to do beware of the addictive nature of the sport