I decided to install small bilge pumps on each side of the trunk.
Not much water gets in there, but I do get some and when I pump it out with a hand pump water goes places I don't want it to and afterwards much flows back out of the pump. These little pumps (500 GPH) are inexpensive and work very well. This one was a little crooked when I shot the photo I see--I'll have to straighten it. I have a feeling I'll need to do that every time before I turn them on, especially after trailering. I see no way to fasten them down, but it's not really a problem. I'm also debating how I'm going to anchor the discharge tubes--no way do I want to drill any holes in the trunk. The floorboards hold them in place pretty well when they are installed, so I may just put a couple p-straps in the stringer at the top (want the tubes to go straight up, then back to the cockpit) and I see no problem drilling holes up there.
Pete McCrary put a single pump in front of the trunk but I find, at least on my boat, that water tends to accumulate in the compartments aft of the ballast. This is good because I don't have to remove floorboards to get at the pumps. The little pumps I put in were $35 each, so not bad.