After looking over all the suggestions and options, I'm thinking that Brian's foam set-up might be a safer set-up for unplanned wet exits or re-entry and rolls (which I can only do with a paddle float thus far). After thinking about a bungee D ring set-up, the bungee will not be tight against the fiberglass as it is on the outside of the boat. There will be a gap as it hands down a bit, dependent on the D ring size. That gap might be concerning.
The hanging foam in Brian's set-up could probably easily break off if needed in an emergency.
FYI - I did not mention in my initial post that having 2 low volume boats means the pump can not be stowed between the seat and hull. I no longer want it bungeed on the outside.
Exactly While I do use the block and bulkhead combination in my own boats, the majority that I’ve outfitted have used two block. They’re easily installed using contact cement.
The absolute worst case scenario with the foam blocks is that you would kick one or both of them off in a panicked exit and have to find an alternative way to carry your pump for the rest of the trip. There is no way you can get hung up on them. Additionally, the pump is held high enough that it's actually difficult to hit it with your feet, especially since it's along the centerline of the deck.
BTW, depending on the design of the seat and the pump in question, storage between the cheek plate and hull may still be possible in a low volume boat. I do that on both my Pintail and Anas Acuta.
ease of access using foam blocks is a very accessible method for just the pump but there’s a way of anchoring a mesh bag or flat sheet of plastic with bungies through four anchor attachments that also works. The problem with just using bungies is that the pump doesn’t naturally slide under the bungies but if you have a flat surface for the end of the pump to slide against you can slide the pump up and in securely.
the method for securing bungies is with a 4" piece of 1" webbing folded over and epoxied to the underside. You get to that area but turning the kayak over, mark four 1 1/2"x1 1/2" areas that are sanded/roughed up with 60grit. Apply epoxy to 1" section of overlapped webbing and onto underside of deck. Position loop of webbing over sanded area and weight with platic covered brick. If the deck is peaked all this stuff will slide to the middle so you’ll need a couple plastic tape covered bricks in the middle holding things in place. When cured up attach your back/plastic sheet to the webbing.