Hello, i needed this set quickly for a special project and have only dealt a little with other systems. Unfortunately, this also means that you probably won't find anything really suitable. But if you tell me exactly what you need, I might be able to help you.

I appreciate the info, as well as the offer. Unfortunately, I am not quite sure what I would need. I am just piecing things together to make a belt driven robot arm, and I just have been browsing around looking at different things and if I spot something that might be useful, I try it out. As such, if I do need something, I would not even know what to call it until I find it. I have made the frame work find up to now with the pieces that are available, I was just hoping there might be more I could look at in case something jumped out at me as useful. So no worries, so far so good. Countersunk M5's have worked well connecting things in which the right angle pieces are not ideal.

I did just come across something. I was trying to see if I could take this inner 90 angle piece and using Orca Slicers tools, remove/negative out the bottom part that slides into the rail so that one of the outer edges (as seen in the image in which the piece is white, then you can see an example of how I was trying to use it in the photograph) was flat so that I could mount something flush to it, when I noticed a few areas that had pretty gnarly vertices which were making the object non-manifold (arrows pointing to the ones I noticed).

Hmm, they might fit, but you have to try it, i made bolts to fit without the need for nuts, due to lack of interest i did not invest more time in extending the functionality yet. But if you need a specific part, I would add it.