2 things I noticed:
1) I'm confused as to why 5 links isn't possible for you. Is there something preventing you from using 5?
2) I watched your video. I noticed that the derailleur didn't seem to rotate back at all. I'm not in front of my bike right now, so I can't comment definitively on how mine works, but I'm pretty sure the derailleur rotates slightly on its first mounting arm when torqued properly. Mine happens to not rotate very well, so I have to manually pull it back a little to make enough room and if I overtorque it even a tiny bit it will stay in that position. Which, I believe, is how I leave it because it actually doesn't matter if it stays there. But, if it rotates forward too much or is torqued down and stuck in the forward position, it might not clear.
Hey regarding point 2 on this guidance. I'm not experienced or capable enough to understand this issue and can't see the possible problem you described. I can say that I understand the high and low limiting screws which prevent overshifting outside the available space on the cassette, and I understand the b screw that acts to flatten out and open up the derailleur. The high and low limit screws aren't causing a problem as the setup shifts to the highest and lowest gears, and not beyond. The b screw has been set in various positions, and I can't get smooth shifting past gear 3 onward to 2 and 1 and back again. It's just terrible no matter how I adjust the b screw and per-gear in-app adjustments. The derailleur is mounted securely on the derailleur hanger. Nothing that I'm aware of is bent or damaged. So, I don't know what else I can do.
Here's where I'm at with this phase of the project. It doesn't seem to be viable for someone who isn't Trace Velo or one of you guys to be attempting an implementation outside of the manufacturer's specs, so I'm giving up on that.
Maybe someday I can try again to get this particularly nice 10-50t cassette to work, but for now I'm going to try the VG sports 10-46t item which I ordered from Amazon. I didn't go with the sunrace product mentioned above because it was said that the black one loses its coating, and I don't want an all silver cassette if I can avoid it. So I went with the VG sports product at a much higher price because there's one good review on Amazon for it by a guy who sounds like he knows what he's talking about. Still, I'm probably overpaying at $175.99
Anyway, I'll say this to anyone reading this thread. Don't go with an XD freehub. There's something like 1% availability on cassettes compared with HG.
Lastly, all of this said, I have to admit that I have never in my life been able to get a derailleur to shift well. I've always had to take them to a bike shop. It annoys me, and I always felt powerless about it, and this is a big reason why I wanted e-shifting, so I could dial in the shifting using the per-gear fine adjustment capabilities.
As much as I did NOT plan on doing this, I'm thinking now that it's worth a trip to the local local shop to see if I can persuade them to work on my local shop subverting build and see if they can get this damned gear 2 to shift right.
Yep, I'm thinking I'm going to do that.
