Do you already have a "grab line"? If not, you might want to consider (in addition to your bungies) a line just above the sheer line, all the way around the boat (or separate lines around bow and stern), to hold on to the boat when you find yourself swimming. This should not be bungie; you need non-stretchy rope with just enough slack so your hand fits in easily.

The chart I clip by the corners so it lies over my sprayskirted lap, and flips forward to exit.

I use a camelbak--the kind with the little accessories bags attached--as my deck-bag, and no bungies (I tie the bag to four deck fittings with non-stretchy cord, and clip the chart to the near pair of those same four fittings). Myself I'm through with bungies altogether; I've lost too much stuff in surf. If it's under a bungie on a rough day, it's just temporarily yours.

I used to use a camelbak in the cockpit, and used bungies with everything backed up with tethers, and then I took a bad dump and had myself in the water looking like Gulliver with the Lilliputians holding him down with strings everywhere. Now I try to keep everything possible either off the deck or zipped in a compartment of the camelbak. I don't put anything in the cockpit but me.