For electrical insulation and keeping water, dust out of the battery racks, each will have a polypropylene cover. I purchased some 1/4" thick polypro at a local plastic shop. I used this blade on my circular handsaw to cut it up (I found that Sharpies mark on it acceptably for guidelines):
Here is the front cover in place, with the hold-down bolted down over it:
Here is the view of it from below, with the hood closed. Very, very close to interfering - but it does not interfere:
This is a closeup of the threaded rod going into the top hold-down as well as the outlet hole for the 4/0 welding cable. The holes that the 3/8" rod go through are 7/16" in diameter to provide for just a little "slop" in getting the rack on (without that, you pretty much have to get all 6 holes lined up perfectly then drop the top on exactly vertically):
I also cut the cover for the lower rear rack. Here it is, with the hold-downs placed on top of it for effect:
I have a few more holes to drill in the upper rear rack and the under-seat racks, and then it's time for paint for them. Getting very very close to wiring time...