I was pondering if one could use a V shaped router bit and router table fence to turn a t slot into a v slot on some of the larger 8020 style extrusions. The slot dimensions would different and so require different wheels but build concepts would be similar and one could scale up current plate designs. Ostensibly cheap than using openrail on the extrusion. Would the machining of the slot created metallurgical problems? If one used large enough t slot perhaps a piece of angle iron could be dropped in to create a steel rail?
I think you would be better off adding linear rails to it. A long time ago, someone on this forum bonded round steel rods to the v-slot so they could utilize steel v wheels running on top of the round rod. It worked. I don't know how well, but it worked. Here is a picture of the idea: Search steel wheels in the search bar. If you want to make your own v rails from steel bars, watch this. How I Grind V-Rails - CNCnutz Episode 134
Here are a couple of concepts that have been on the forum for many years. The second could easily be applied to 8020 sections. The first eliminates the need.