Yes, that's Jerry Works' stuff - really great read with tons of ideas. I copied his squaring sticks idea, but they totally block the t-track channel in the table side profiles. Using either Rexroth or 80/20 you get t-track channels along the top and outside of the profile, which I find is a plus.
I believe Richard (A?) at Rip Dog uses 80/20 - 1515 - ULS (1.5" or ~ 38mm), and I think that lies flat, allowing for more optimum clamping as I described above. But I'm not totally sure of this, nor am I sure if the additional 2mm if using 80/20 40-4040 UL or Rexroth 40mm will work.
I have some access to Rexroth Bosch profiles thru my son, so will see if he can find some 40mm Rexroth profile stock. He mostly uses the 45mm profile, which I now know for use isn't optimal.
By "dropping" - actually sliding - the x-section of the Rexroth into the top V-groove which shows up a little in the pic I included, you gat a fantastic connection. By fiddling with a "straight" straight edge - I use Woodpeck, you could use Veritas or anything else - and some Qwas dogs You can achieve co-linearity between the 2 attached tables, which facilitates ensuring the FS1900 guide rail is square to the fence.