Best vendor for ~300Ah cells? And some related questions

[sailingharry]

I have a 43' sailboat, currently with 800Ah of AGM. Over the last 3 summers, I've been aware that they aren't long for this world. Yesterday, I used a heat gun with the inverter, and in under 5 min I had a "low voltage alarm" -- and my batteries were at 100% SOC when I started. Not sure the Admiral is going to like that when she tries to brew coffee! So, the "some day" LFP upgrade is "NOW." Some background:
* Daily use is ~250Ah
* Peak normal load is ~125A for coffee, or toast, maybe 10-15 min per day.
* Peak theoretical load is 400A (but realistically, 250 if you run both toaster and coffee together)) Master fuse (and wiring) will be 400A.
* AirCon is a potential future load (but not present yet), maybe 200Ah overnight.

My current plan is a 600-1000 Ah bank (2-3 days autonomous, but much less if I install AirCon), with an Electrodacus BMS.

So, cells:

A 3P4S of ~300Ah cells sounds like a good choice
I think I like the "grade A" EVE LF304 from 18650. I can get 8 for ~$1K, 12 for ~$1.5K.
I think I like the "double" terminal style.

Questions:
18650 sounds on here like the go-to vendor. Solid, dependable, (mostly) responsive, with cells that are as promised. Still true?
Sure, I'd like to save $100 if possible, but really not too concerned. Is this currently a good price, or is there much to be saved elsewhere? Docan? If I can save $200 and take 2 months longer, I'm not interested.
Are those double terminals the current rage?
How about bus bars? 18650 sells flexible bars to fit, but only for 2 cells each (not ganged). These are ~$6 each, or nearly $200 for a 3P4S bank! With a 3P bank, the (S) bus bars take all the load -- can they support 400A? Is there a better answer?

Let me hear your thoughts! And trust me, I'll be back with more questions....

 

[sailingharry]

Already new questions!

For my space, an ideal arrangement would be 3 wide sets, one after another (3P4S), which would put 3 terminals side by side. Then each "interconnect" would be 3 connections wide (12 holes) and 2 deep (from first set of cells to second). This would in a theoretical world be a single copper plate about 9" x 2" with a row of 12 holes down each edge. Not sure that's an ideal way to do this. How would you connects 3 cells in parallel and series joined like this? In laminated copper, they sell a 4-cell strip that could be used to parallel them and then a wide strip designed for end-end connections. Either parallel both cell sets and connect with one wide strip (center cell) or parellel one set and then jumper with 3 wide strips. Seems like a pile of connections!

+++
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interconnect
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etc


And at each end, I'll be connecting some 4/0 cable. That's potentially a lot of load for M6 fasteners. Any "best practice" for connecting a 4/0 cable to an LFP terminal?

Also, what screws to use? Stainless seems to be the go-to. In the boating world, stainless screws in aluminum is a corrosion disaster. These are inside, and probably greased, so maybe not an issue. Does the AL/SS cause problems?

 

[hwy17]

Ezealco is good. I would choose based on distance. Ezealco can ship to me cheaper because they're in Texas and 18650 is somewhere east.