Gt Grade for amateur cx race?

I race cross on clinchers as do quite a lot of the field. It depends on the course a bit - if it is through woodland and there are exposed tree roots and the like then I would err on the higher side for pressure. In mud I run below 30 psi. For a standard cross course I run around 30-35 psi depending on my tyre width, but to be honest I would be quite happy running higher pressures if it was a grassy criterium as some summer cross courses are.

I weigh about 75 KG for what it is worth. I can't see why you would think the Grade is too fragile. You would be riding on grass on low pressure tyres, not smashing your way through a rock garden.

With your user name including 'terrier' are you doing a YCCA summer cross - e.g. Middleton Park?

I've done a couple of CX races on my Grade (Carbon 105). Running Schwalbe X-One tyres tubeless at 35psi worked really well. I'm a fat sod, so if you're not really heavy you could probably go lower on the pressure if you're running tubeless. Even at 90kg+ i think I could have run 30PSI ok.

The bike is more than robust enough to deal with CX. The biggest problem I had was with gearing. The semi compact chainset meant that I was fine in terms of low gears (36-32 is as low as you'll get on an out and out CX bike most of the time) but the 52 tooth big ring was just too big (not that you'll be wanting to use it much in a CX race).

If the course is relatively dry it will work great. If there is heavy mud then the clearances on my grade are not brilliant, so you may get slowed up a bit by mud blocking the tyre

I did a race last december on my Cannondale Synapse Disc with 30mm CX tyres fitted. I knew it wasn't going to be epically muddy as it was a fairly sandy course so the reduced clearance (compared to a pukka CX bike) wasn't an issue. I'd imagine a summer series race won't be an issue either.

comfort and grip? you're getting cyclocross all wrong

it'll be fine and a lot quicker than a full susser around a summer cx course