shmbry wrote: What is the usual practice when you need to work on the underside of the hull? Should I continue and fit the floor and replace the deck and then turn it over when the boat has it's full strength?
I don't know that there is a "usual practice" for that but in my experience, most people don't turn it over to work on the bottom. If the hull is too big to easily turn over, leave it upright and get it onto blocks or jack stands so you can work from underneath. Having said that, I have turned over boats that weighed several hundred pounds with the help of friends and/or mechanical aids. In those cases, I made sure the hull and (attached) deck were structurally sound before the turnover. I would say, do the floor and any side structures that support the deck and gunnels because upside down they will be supporting the weight of the hull . Note: it is sure a lot easier to work on the bottom when it is upside down so the extra effort to turn it over was worth it to me.
JerryF