Man, this thing is a beast! Still, it's lighter than I expected, and it will fit in my backpack which means it won't be as difficult to get it to the lake as I'd feared.It takes 23 hours to fully charge it, and kept my laptop running for nearly 3 hours. Hey, for lead acid batteries that's pretty good, and laptops are energy hungry.
I now have almost everything I need. Still need about $30 for a power drill (I have the correct diameter drill bit though!) and the marine sealant (coming in the mail). Then I can drill the holes, seal the tube ends into them, fasten the enclosure to a weight, and test the entire apparatus in a nearby public pool. It's getting colder, few are using it, I should be able to get some time to myself. But wow, will I have some explaining to do if anyone catches me.