Adapting rear mudguard?

I ride an old Suzuki GN125, I live on a narrowboat. When cruising my bike lives on a rack I had purpose built, on the back of my boat.

This all works fine but the boat is 6'10" wide. I need to remove the rear light cover, bulb and its carrier in order to bring the boat down to around 6'2" long. This prevents potential disaster, if the bike came in contact with lock walls.

I've toyed with the idea of getting another, slightly shorter bike but it seems daft spending money when the elements are going to destroy its value. So, in order to save time and messing I've thought about adapting the rear mudguard. The idea is to cut through it forward of where the rear light assembly fits to it. It should then be a simple task to move it out of the way when approaching a lock. I thought about fitting a couple of hinges to join the cut sections and then a slide bolt or two, possibly under the mudguard rather than on top of it (aesthetics) to lock it in place while riding. I need to check if there's enough flexibility in the wiring of course.

Before I go ahead I wonder if this might lead to an mot failure (sharp edges). If so it's not really a problem, I can buy a new mudguard for thirty quid. I was also wondering if anyone has any other idea how I might go about cutting, then piecing together the mudguard?

Thanks for any replies.