It's not the insulating properties that I am worried about...
It's that Phil's solution is using the factory box material as a 'washer' and the cables are being clamped on either side of that 'washer'. Most likely it will be plenty secure and over time the 'washer' wont crush a little and allow a little loosening/play in the clamping force and lead to a poor connection which will then get very hot with the high currents that flow through that path.
The bulkhead pass through design doesn't rely on the plastic box for an electrical clamping path, only uses it as a mounting path for the pass thru's plastic housing. That's why it would be a good solution.
Anyhow, Phil has tested his method and has stated it hasn't been a problem so likely it won't be a problem when lots of installs are done. Just make sure you tighten down well and maybe check once a year.
Of course one could add belleville washers for good measure
cheers,
george.
The only thing with the fancy post bulkhead terminal, is that it has a basic electrical fitting lock ring, these are ok for putting EMT or BX fittings into thin commercial/residential grade galvanized boxes, but Im not sure they will handle the vibration in an engine compartment as well.
There isn't alot of thread engagement on those lock rings and the threads are plastic on one side, much easier to strip the plastic threads and you cant torque down on them as hard either.
The galvanized metal lock ring on that is just cheap stamped metal, quite flimsy compared to a 5/16 (or whatever) nut and bolt, and your only getting a thread or two of engagement. I have stripped a few, mostly on BX or EMT fittings which are cheap pot metal or whatever.
This might be better for battery connections through a fire rated box in a fixed UPS system or something.
Plus it has two flat sides, so you should make an oblonged hole so it wont rotate, which is good I suppose, but more work, You essentially need to drill two smaller holes and take a bastard file to it if you want to make use of its purpose.
In terms of crushing the battery box material and then getting loose nuts/bolts, that might be an issue, we'll see what LCP's experience is. But it could be alleviated with washers a few different ways, by increasing the surface area under compression by putting washers against the battery box is one way, though I really really doubt it will ever be an issue. He could also overdrill and put a sleeve through with washers on the other side so it isn't under compression, but I'd probably use a nylock nut on one side and never worry about it.
If your the george that makes all the cool LED lighting, you should consider buying and selling the fusible links with a LED indicator parallel to the link, and connected under the eyelet ends, as an indicator for the links if they've popped.
I think you could get an LED with wire soldered, to reach the eyelets, and then heat shrink them on top of the loom. If a link popped you'd have a light indicating it popped. It could be easily done to the $12 factory part, and the old one could be thrown in the glove box as a spare. Kind of like the LED indicator fuses.
It would be really really easy to see if the problem was a fusible link without baring wires and a voltage tester... I think it would be a worthwhile (worth the cost) upgrade and you could retain the old one as a spare.
I'm guessing your familiar with the automotive fuses with an LED indicator, but with a fusible link..