Access can often be created
Tom,
I have no direct experience with your boat model, but have added some access plates to parts of our boat that
greatly helped with maintenance projects like the one you face.
Maybe a section of an inner panel needs to be made removable.
Usually the perimeter of some piece of paneling that's tabbed in is "structural" but the center of it can be made into an access plate.
Be sure to measure several times and then be extra sure that the reverse side of the area is clear before using a bladed saw.
Actually this is an excellent excuse to buy vibration cutter like a Fein Multimaster. This type of tool makes safe and controlled cuts easy.
(Poor folk make do, for small projects, with a cheap knock-off from Harbor Freight. It's 90% cheaper and about 40% as powerful... )
I speak from personal experience -- I did get what I paid for...
Regards,
LB