So I read the post you point to as the reason for selling and I'm confused, hopefully you can help me out.
Is this the kit that works with panniers?
You mention drilling and tapping holes for reflector mount, does the one your selling have the holes drilled in it?
1) Neither work with the stock signals and panniers as far as I know. The one I have for sale has a longer bracket available for pannier use, but the one I have for sale has the shorter "tail" bracket. I understand it will work with aftermarket signals (e.g. Rizoma). I have not verified, as I have stock signals (and no panniers). The one for sale does hold the signals out from the rear end farther. It holds them out with the plate and it may work with Panniers and the stock signals, not sure, never installed it and again, no panniers. If you follow the link for the install doc on the for sale tail tidy, I think it shows the longer "tail". I'm sure you could order that if you wanted.
2) The "drilling" was done on the one I kept. So I could attach the stock license plate holder that has the reflectors on it. I drilled and tapped 2 holes. The one on my bike (not the one for sale) is weak at the LP mount. The plate only gets picked up by 2 holes and that's all. I wanted the integrated stock side reflectors, so I used the stock LP holder with this mount. The one for sale has a full (all 4 corners) plate holder as shown in photos.
The one for sale is brand new, unused, unmodified in any way. As pictured.
Let me know if you have any other questions. Thanks, Scott. Welcome to call and chat about it if it helps.