Hello Maarten,
Welcome to the UKW and thank you for the kind words.
Here are the replies to your questions:
1. I didn't think of an easy way to tie the side panels to the catch tray and didn't want to add another section of 40x40 extrusion on each side. Additionally, the 10mm thick catch tray fits inside the vertical 40x40mm supports, so I would have to cut "wings" on the sheet to fit in the additional extrusions for support. This certainly could be done, but the lack of side access to that part of the catch tray hasn't been an issue.
2. I don't think there would be any issues with replacing just the end pieces with 40x40mm extrusion, or even the two long top horizontal pieces. I used the 80x40mm on the four sides because I wanted two channels along the top for attaching brackets and clamps. I can still fit my chubby arms anywhere on the catch tray.
3. Your suggestion sounds like a great idea to utilize dead space! My workbench has about 12cm of space in the center between the backs of the Systainer trays. This can be extended to about 18cm if the slide trays are positioned near, but not beyond, the front edge of the 40x40mm vertical supports. I made sure none of the drawers or trays extended beyond the front edge of the supports so they would not interfere with anything clamped to the supports. I also had to change the two duplex outlets on the sides because the plastic housing prevented me from clamping large pieces to the side.
4. I just edited the first post in this thread to add the SketchUp SKP file and the Item24 PDF. I use the free 2017 version of SketchUp, but the file should be compatible with other versions of SketchUp. Unfortunately, I can't convert the file to DWG or any of the other CADD formats.
I am very happy with the slides. I saw the slides on the German Amazon site below, but bought them directly from the vendor because they were less expensive with free shipping.
https://www.amazon.de/Vollauszüge-T...hienen-Teleskopschienen-SO-TECH/dp/B07Q28F82N
Here is the link to the slides from S&O Handelsgesellschaft mbH. I used 400mm slides for the side Systainer trays and 500mm slides for the four end drawers.
https://so-handel.de/36842778.html
I still have the router template used to mill the keyhole slots into the extrusion. You are welcome to it if you want it, and it should work with any extrusion. However, I made the template for use with the Festool OF1010, Festool 484176 13.8mm copy ring, and 8mm carbide cutter. I bought two of the carbide cutters, but never used the second cutter. You are welcome to one of the cutters as well. The extrusion is easy to mill using a router and carbide cutter and making multiple passes.
I don't have the router template for the Systainer trays, but have eight spare trays in 19mm plywood you can have. One is for the original Systainer footprint used by the VAC SYS and the other seven are for the next generation of Systainers. All but one of the trays is painted and ready for installation. The unpainted tray was my router template test tray and I forgot to paint it.
If you are ever in the Frankfurt/Darmstadt/Mannheim area, please let me know. I am happy to let anyone visit and exchange ideas.