There are a few side mount builds on the non-rail side only, but AFAIK I am the only one that has side mounted both the rail and non-rail sides.
I provided a few details on this thread, but I ran into some technical issues with my SKR Pro controller that I have just finished sorting out, so I haven’t had a chance to fully photograph and document everything yet.
If you want, I can try to send you the 3mf files in a PM, or I might be able to figure a way to share the Fusion files somehow… Not sure if that will work, or if I have to post them in Printables instead. This weekend and the following week is a bit crazy (retirement starts today, birthday is Monday, family is in town for a wedding, lots of running around for personal stuff, etc.), so it might take a few days or longer to get everything together to pass along to you.
Edit - sorry, re-reading your original post, I think I misunderstood your request. I thought you were asking about side-mounting the belt on the Y rail side of the table, but it seems that you are asking about mounting the rail itself flush with the table.
Nobody has done that AFAIK, and it would take some serious redesign of the YZ plate, (the rail would be lower, so you would have to lengthen the plate to have the roller bearings lower while maintaing the Z lead screw aty the original height. I think that you would also have to redesign the belt drive system to compensate for the difference in both the Z plane and the X plane. (I’m not saying this clearly, but if the rail is moved lower, the Y motor housing would be affected. If you move the rail closer to the edge of the table, you will have to figure where and how to mount the belt)