The floor needs side joiners and stringers to tie all floor components and achieve a solid deck, as you don't have a refereence or templates to work with is a sad story. You could made a wooden deck, but don't expect that nice sib to work as factory same unless you find a good Samaritan that can send floor, joiners an stringers specs to duplicate at a wooden carpentry. Or check with Defender if they stock a complete original wooden floor kit for that Avon model, but that could be costly..
Happy Boating
