Thank you very much for your replies and sorry for not responding for so long...
I wouldn't really like to put a hatch in the deck, i just like it as it is.
Cutting away the deck - is it the only way to go? What about injecting something into the laminate?
And if I'll have to cut the deck? Could it be done from the inside, leaving the outer side untouched? What tools can this be done with? The deck seems really thin, I'd suspect that it is not that easy to separate the layers without destroying everything...
Thank you very much for your help, I really appreciate your replies!