Open cockpit on rhino

Hy everybody, I just need a little tip on rhino. How would you do an open cockpit on rhino, that would cut both deck and transom. I've managed to do a box-shaped cockpit but do not know how to do an open one (type VO70,...). Thanks for your help

 

If deck and transom are closed now (ia it is after a typically iges import?), you can make the cockpit sole and sides as surfaces, let them extend out in the open and the use it to trim both deck and transom. Alternativelye you could model the deck and transom with the openings in the first place.

 

I don’t know Rhino that much but most cad have a trim command. Place cockpit on boat then trim out/off the bits you don’t want.