The floor becomes more solid...
Passenger's door ... step? sill? thing? Mostly welded in.
Mostly sorted out the passenger's footwell side of things. Need to grind up the welds of that inner face, but we're mostly there now. One little patch of rot in the remaining floor panel, right on the corner of where the wheel-arch curve meets the new metal, to excavate.
Working my way along to the back of the cab, and the passenger's seat-base:
That divider is mostly solid, but the side where the battery box was previously is incredibly lacey, and I've already cut so much out that it's not the end of the world to rebuild that as well.
A cheap second-hand injector was also ordered from the bay of E for mockup & tinkering purposes (Bosch 0-280-156-061, as found in various VW products. 316cc/min or so at 3bar, high impedance.) even though I'm still noodling with manifold thoughts.
It did confirm that 14mm injector O-rings fit very nicely in 12L hydraulic compression fittings. (Extremely snug in some more than others, which is probably manufacturer variance), which is good news.