Here are a few pics of commercial boats which may help to visualize the situation for pump & bottle storage.

First, a Mariner Coaster with a seat hung from the coaming:

The other side, on the Coaster. Here you can see the foam inserts that the Broze brothers glued between the hangers and the hull to keep the seat from moving sideways. Using an appropriate size holesaw, you can make a good friction fit for a pump or a 'water' bottle.

Next, a Mariner Express with a sliding seat. The side flanges are shorter, but there was enough for me to drill a couple of holes for shock cord which is anchored to glass tabs I stuck on the hull. Pump and bottle storage.

Last, the Romany. You can see the foam pads which cover the machine screw heads used for attaching the seat to the hull in the Romany.

As the hull gets narrower and the cockpit less deep, the potential for storing stuff on the sides 'goes away'. (This is certainly the case with my Bjorn Thomasson Frej and Panthera, both of which are nice narrow boats with low cockpits).