Darn, the silly forum logged me out while I was writing a post.

Long story short, I've made a clone of my outer ear and the pouch mould. Had to made new impressions, as Mold Max 60 is too hard/brittle for pouches and holds on to impression silicone way too well even with unsealing agent. Removing that would take eons if it's at all possible.

Body doubling is tricky - have to use huge amounts of vaseline (incoming nasty jokes) so that the hair are safe. First time I haven't applied it everywhere the silicone flowed... that was quite painful.
In the final and decent (but not perfect) attempt the silicone was applied by a friend - he made a few minor mistakes though.

Both Rebound 25 and Body Double are extremely good brushable thixotrophic silicones, but I could use a working vacuum pump to remove air bubbles. With the aid of Smoothie surface smoothening spray, I can fix any minor issues by hand pretty well, should they occur.

Pouch mould will be used to create a silicone shell (again out of either Body Double or Rebound), which will then be used for installation of the tubing, dampening and the driver.
I'll attempt RE-400 first - but I need to fix a broken trace there. Should that fail, TWFK from Brainwavz B2 is on the standby, with a slightly more aggressive dampener than the original one.
The requisite ear canal volumes until the second bend are: ~1 cm^3 for RE-400, ~0.33 cm^3 for TWFK. I'll compute the exact placement and tubing based on the 3D model made earlier.

This means a shallow insertion on RE-400, even slightly shallower than with long RE-272 biflanges. To achieve that, I might have to rotate the driver and bend the tubing into an S shape without kinks or create an acoustic chamber larger than the tubing I have. (Largest diameter is 5 mm inner.)

The ear doubles are for the ear and cheek simulator to be done later.