I thought i would share this idea which i have never seen in any of the books or magazines related to boating.
When our 50' Narrowboat Progress, was a drawing on the wall in our house it grew, shrank and changed configuration by the week, if not by the day. Obviously you need to commit to a layout when you order your shell so that the windows, portholes, hatches etc are in the right place.
I have quite a good spacial awareness but my idea was to take a ball of string and a packet of tent pegs to the park (our garden is not big enough) and to peg out the design full size on the ground.
This enables you to literally walk round the design and get a feel for it. you could go one stage further with large cardboard boxes to represent bulkheads etc.
This gave us the confidence to go ahead with the design and we have not regretted it.
I hope others can make use of this.