Some years ago I waterlined an Atlas HMS Rodney for one of my grandsons.
I've still got the scars on my fingers I think.
I built a jig - a wooden base an inch longer than the length of the model with two parallel hardwood strips nailed to it, the gap between them being Rodney's beam, and the beading thickness being the amount I wanted to cut off. I could then rest a hacksaw blade across the beading strips. I found that a junior hacksaw blade wasn't man enough and bought a 12 inch hardened (for stainless steel) Eclipse Predator blade. That worked fine, I just held the model in place and cut half way along the model, then turned it round and worked back to the middle.
It was really tough.

https://imgur.com/a/1t02Ans

As you can see I've still got the hull - one day I'll find a use for it....