Well,
I'll more than likely get a bit of flaming for this but, no biggie, been flamed many, many times both in my career and on here. Anyway, I changed from (3) 12V Junk INTERSTATE batteries to (4) Costco 6V Golf Cart batteries over 7 years ago and, since I have very, very little clearance above the batteries, I have NO HOLD DOWNS at all on those. They weigh 67 lbs EACH!!!!!!!!
Those (4) batteries are very close to each other and have a small spacer in between them so to just keep them from POTENTIALLY from sliding around. Now, am I gonna BOUNCE them out of their somewhat secure position, with any sort of rough road or intersection? Nope, not gonna happen. As stated, they've been that way for almost 8 years and haven't moved one micro inch.
Scott