So, on measuring my current bike, I have 20mm of spacers. So the 56T Strael is only 5mm taller in terms of Reach, which isn't really a problem I guess. Now the next thing is to work out a headset that doesn't add another chunk as @jupiz says. The options from Fairlight are FSA Orbit (looks huge on top of the HT), Hope or CK (can't afford). Or can I just get a machined third party top for the headset for max slammage?
Your Genesis is definitely a closer fit to the 56 Fairlight, any road bike which requires a 80mm stem to make it 'fit' probably isn't a solution - unless you have a particularly short torso / arms. And yes 80mm will make it Twitchy AF - it already has fairly aggressive angles for an all road frame.
So, on measuring my current bike, I have 20mm of spacers. So the 56T Strael is only 5mm taller in terms of Reach, which isn't really a problem I guess. Now the next thing is to work out a headset that doesn't add another chunk as @jupiz says. The options from Fairlight are FSA Orbit (looks huge on top of the HT), Hope or CK (can't afford). Or can I just get a machined third party top for the headset for max slammage?