Well that went a hell of a lot easier than I expected!!!
The old adage of "measure twice, [or 5 or 6 times!] and cut once" was in full effect!
I was a bit twitchy about going too close to the underside of the hull and because the layup is so thin, I took a few precautions...... Once I'd marked out what I thought was the correct location on the outside of the hull with a marker, I just shone a torch on it and stuck my head inside the hatch to see if it was going to foul the hull. It was close but okay!
Enough mucking about on it for me tonite though I think. I've had some cr@ppy virus all week so I will leave the rest until tomorrow.

Cheers!
Phil