You need one of these.
This:
or this slightly bigger one:
First ones rated at 300A second at 500A I believe. You will probably need one with a 5/16" stud as I'm sure the hole size is the same as an RX-8 even though I've never measured one. This would also give you a location under the hood to add to the positive cable.
If you want one let me know. Either style can be black or red. There's not really and coverings that will fit with that fuse block hanging of this though. I checked already. If you want to oversized the hole to 3/8" I have a couple of these right now sitting around for general usage. I should probably put them for sale on my website but I was waiting for the stainless hardware to show up before doing so.
Anyways PM me or email me