ATF has lots of nice seal conditioners and is about a 15W oil. We used lots of ATF in our dirt daze, for the very reasons you described. Thicker oil can be obtained by mixing in varying amounts of 30W to 50W, in a manner akin to "Mixing big marbles in with smaller ones" in the words of Rick Sieman (aka "Super Hunky"). Motocross stars can opine long on oil viscosity nirvana, but for the rest of us mortals if the forks aren't going rigid or slamming stop to stop, it's probably close enough.
You are quite the invertebrate tinkerer, did you ever create & install some fork drain screws in your tinking?
No, I haven't. I have to admit that I have not fooled much with front forks during my life of other tom-foolery. Their innards are a mystery & I've never had the actual pieces in my hands although I do understand how they work. When the guys here who really know what they're doing talk about drilling this & grinding that, I cringe. Like you say, if I don't get the bars ripped out of my hands or my thumbs broken hitting a small pothole, I'm good.
I may tweak my headstock a bit also. I've noticed a slight klunk when coming off the centerstand although there is NO klunk when I hold the front brake on & honk the forks up & down. And I never hear a klunk on the road, only rolling off the centerstand. Strange?
It's a fairly simple job on the Enfield; loosen the two clamp bolts & the big Allen, crank to 55 pounds then back off & crank to 15. Tighten it all back up. I'll check Pete Snidal first, of course.
I miss Pete. The first years I had the Enfield ('09, '10, '11, '12) he (& many others here) helped me more than any words could ever express. The bike was an alien to me except for what I had read in books or online & it arrived in my driveway brand new, but drained of fluids, no battery & every single bulb (including the flasher) on the bike burnt out. We (the forum) never came up with a theory although it was discussed for a long time.