[sdiy] PCB extenders with a flexible ribbon cable - looking for suggestions on construction method

[cheater cheater]

Hi all,
I need to build a bunch of PCB extenders. Basically, they're two PCBs,
connected with a ribbon cable. I have to build like a 100 or so. Both
sides have gold finger PCB edge connectors, there is no slot on either
side.

I was wondering if anyone had suggestions on how to best do this to
keep the cost, assembly time, and rejects to a minimum.

The specs are:
- The signals carried are up to 35Vpp, tiny current, sub-500kHz, balanced
- Each pcb is 25mm wide (but can be a little wider) and can be
anywhere between 10 and 80mm long. No logic, purely 1-1
straight-through connection. They can have vias if needed, but
hopefully not needed. Produced in a pcb house, not at home.
- The card edge is on the 25mm long edge and the ribbon would be going
out of the opposite edge
- 32-36 pins need to be carried by ribbon. 32 is the minimum, but more
is fine (I'd just carry ground)
- The ribbon needs to be as flexible as possible. what is the most
flexible ribbon you've ever seen? I'm looking to keep BOM cost down
but if the thing is tough to bend like a stick then that doesn't help.
Are more core strands better? Mouser lists a few stranding options:
ones that start with 7 and ones that start with 19. The options seem
to be: 7, 7x34, 7x36, 7x38, 19x40, solid. I assume the left number is
the number of strands and the right number is the AWG. What's better
here for flexibility? The cable isn't going to be moved a lot or
strained, but up to 2 meters of it are going to hang off the
connector. I assume higher AWG (=smaller strand diameter) is better,
and more strands is better, but is 19x40 not going to be, in
aggregate, thicker than 7x38, and therefore less flexible?
- What sort of material should the insulation be made out of to be
(and remain over a few, say 5, years) the most flexible? The options
are: EPDM, PO, EVA, FEP, PFA, Polyester, PE, PP, PUR, PVC, TPE. Am I
right to assume that PVC and Polyester are going to be the least
flexible?
- Are there tools that can strip all wires of a ribbon at once? Are
they good? Are they expensive? Can someone suggest such a tool?

Here's are some construction methods I was considering:

Method 1. Take a ribbon that's been stripped and pre-tinned in a
solder pot with 7mm bare wire sticking out. using a press, pre-bend
the bare wires so if the ribbon is placed flat on a surface, the wires
aren't "up in the air", and clip the leads to size (think something
like the surface-mount leads of a QFP or something). The pcb has
surface-soldering lands on it that will mate those 3mm bare wires.
Take the pcb and lay the ribbon parallel with it, so the tips of the
wires align with the pcb. However, the ribbon should go from that edge
*towards the card edge connector side* which is "the other way" than
you would expect. Then, you stick the whole thing in a solder pot, and
after a few seconds, it's all soldered in place. Add a mechanical
brace around the pcb+ribbon for retention. Finally, bend the ribbon
180 degrees so it's going in the right direction.

Method 2. similar to above, but instead of using a pcb ribbon, use a
hot bar soldering iron tip. Mount the soldering iron in something that
looks like an arbor press, put the pcb and ribbon in, press down while
feeding solder.

Method 3. Everything's through hole, put the wires through the holes,
and put the thing in a solder pot; add a mechanical brace.

One thing that's kind of questionable is whether the pcb is wide
enough to comfortably solder a 32-wire ribbon without microsoldering
needed for bridge removal. If not, I considered putting the ribbon on
a diagonal across the PCB.

Do you think any of that would work? Which method is the best? If
yes/no, what's necessary to make it work better? Does anyone have
better suggestions?

Finally, I'd have to find some sort of enclosure. Basically, I'm
trying to make something that will look like the "cartridge" in this:

http://devkits.handheldmuseum.com/IS-CGB-EMU/index.htm

...but obviously I'd need some sort of cartridge casing. I'd prefer to
buy something that's ubiquitous and can be repurposed for what I'm
doing. Sadly gameboy cartridges are just too wide for my use, at 60mm
(vs 28-30mm being perfect), and I'd like to find something thicker
because I'd like to fit the ribbon inside them for mechanical
retention. I considered DB-15 connector back shells, but they have
those "wings" on the side that the mounting screws go through which I
guess I would have to cut off or something, plus idk if these cases
would be easy to mount a pcb in. 3d printing is an option, but I'd
really like to avoid it, given the cost + maybe they're not as
mechanically durable (it's a connector after all). Essentially i'm
kind of looking for something shaped like the rectangular container of
a PEZ dispenser, so I'd welcome suggestions. It's fine if I have to
lop off one of the sides to make an opening.

Also, after assembling the extender, I guess it would be nice to have
a test harness (pass/fail on all signals indicated by LEDs plus
per-wire LEDs).

PS does anyone know why PCIE slot connectors (like on motherboards)
have those slanted "rasps" on one side? Always found that weird. What
are they for? Some sort of retention mechanism? Curious.