[msterling]

Usually a 1/2" wrench works on battery terminal nuts. Move it a teeny tiny bit, flip the wrench, move it another teeny tiny bit, rinse and repeat.

Re: using only metal hold downs and trays; the original clamp was metal but only held the battery by a ridge at the bottom of the battery case. A metal clamp over the top of the battery would certainly be stronger. I don't think there was anywhere near enough room to do that with the original humongo battery. Like the OP said, it is really shoe-horned in there. There is not really enough room to install a proper vent drain tube with the Interstate battery.

Re: Drain tubes There are drain holes below that have rubber grommets. A tube could be routed through one of them.