I used a slat floor on my first SOF which had a long cockpit (30"). Even at 1/2" thick, the cedar slats required additional supports under them as they would flex more than enough to break (I had to replace two before I even skinned the frame, also broke the first attempt at an additional support). The photo below shows the frame before skinning, I eventually added another support under the slats to minimize flex.

If you use slats thick enough not to flex so badly, you will add some weight. The weight of the floor is trivial perhaps, but all those extra ounces here and there add up quickly. I suppose you could use a wood species with significantly greater stiffness, like yellow pine, but you are going to have a tough time reducing weight even with thin slats. Maybe one could fiberglass the slats to increase stiffness? Or use strips of carbon fiber?

: I have been tossing around something similar to that too. With a large
: cockpit the floor boards are rather long and heavy.