i have a 1436 john boat i want to take the middle bench out and floor the bottom with ply wood. i like the open bottom so i want have to step over the bench to move around . if i do this will it affect the safety of the boat

I would suggest adding a rib

i was thinking of bracing the side by attaching ply wood or something to the other ribs so i could mount rod holders . do you think if they were all tied together it would serve the same purpose

If you remove the bench, you're also removing the flotation foam.

Something to think about.

You will need to add reinforcement somewhere. Anytime you do a modification like that you are compromising the integrity.

Good luck

Removing the middle seat will harm the structural integrity of the sides causing un-necessary flexing which will in turn cause stress cracks at the point where the sides and bottom meet.