I dug out the headset for Best, then realised I had left the headset for Pigdog back on the farm, which means I have no way of knowing how high or low I can position the fork. Without that, I do not know how long I should make the links at the bottom end.
So I broke out the cardboard and made a top strap. I wanted the Pigdog fork far enough forward that it clears the brake mounts on the Best fork, but not so far that the steering gets really weird. My worries about whether there was enough threads on the fork to mount the strap went away when I realised that the combined washer and brake cable mount were the same thickness as the bar I will use for the strap.
Plan A it is!
I then made a link out of a strip of cardboard that I cut to the same width of some unused bar stock I happen to find stuffed in a bag in the kindling stack in our brick barn. 'Kindling stack' is a bit of an overstatement, it is a former animal stall thigh deep in twigs that have been trimmed off fruit trees. What else might I find as I excavate further, I wonder. I keep finding clothes, which is a worry.
Because I am trying to marry up two different kinds of fork I will need to use some spacers to align the links, unless I bend them somehow.
When the fork goes over a bump, that link will move in an arc. This means I either need some compliance at the top mount, maybe by having a hard rubber sleeve around the fork stem, or something like a slot at one end of the bottom links. I cannot say either is ideal, but at the moment I prefer the slotted link idea because it at least limits the direction in which movement occurs.
You can see below that the way the fork leg expands makes it difficult to get the link in close, especially as the axle centreline is lower than for the other fork.
On the up side I found a really long rear axle plus a front hub shell big enough to take it. I generally strip all my unused bikes down to the smallest parts, so that I can select parts by simply shuffling through my store.
Well that is how it stands at the moment.