Ali,
I do not believe that the grid spacing matters that much. I haven't seen anything indication that 96mm is critical. See my post two above yours (#19) for all the details. Since I felt I just could not comfortably work with a full sheet of MDF as my workbench top, I knocked off a full foot from width and length (actually 13", since the MDF was a 49" X 97" sheet). Since 36" and 84" are multiples of 4", that made sense for spacing.
I believe Ron Paulk used 3/4" holes on his workbench, and there are a lot of 3/4" benchtop accessories. Also, watching his videos, he uses the holes primarily to drop clamps through, and therefore 3/4" versus 20mm is not much of a concern. I watched is video on the fences (rails?) he adds to the long sides of the workbench, and I am going to add the same to mine. I like the idea of cutting thru sacrificial boards to preserve the top.
My workbench top goals were twofold: 1) be compatible with the Festool/MFT "standard" as much as possible, since I am new to track saw usage and Festool, and 2) design for use with Qwas Dogs, which I purchased prior to building the bench. (I had seen a several of Paul-Marcel's videos. and he convinced me I needed to buy them!) Having a Qwas Dog in hand prior to milling let me fine tune the milling to make the 20mm hole as near a perfect fit as possible.
I do have some Bessey 3/4" bench clamps with quick release clamping nuts, and they work great in the table, since 20mm is just slightly larger than 3/4". A snug fit is not needed, so this package of clamps I've had for 5+ years finally got opened. My other workbench had no bench dog holes.
I've looked around at all the 3rd party accessories offered by several FOG vendors, as well as woodworking stores like Lee Valley, and there are a lot of options out there for 20mm, as well as the 3/4" products that have been around for quite awhile.
Other uses: I plan to use my workbench a lot as a clamping table for cutting/serving boards, picture frames, etc. This is where I think the size will really be an asset. I've also never had an outfeed table for my table saw, and this will make its use much simpler. My next project will be a cart for my DeWalt planer that can be rolled up next to the workbench. It currently uses the floor and a couple boards as an "outfeed table". I've been doing that way too long!
Finally, I appreciate all the positive comments. I just ordered a TS55 REQ last night, so I am anxious to try everything out. I guess I can put a list of Festool products in my sig line now ...