This heavy-duty bracket is perfect for making bigger keyboard tray that has also plenty of space for mouse movement. Furniture board that I used is 86cm x 30cm x 2cm.
Whole assembly feels very sturdy. The idea was to only print it once.  :)

Printing: 
PETG
0.24 layer height
4 walls
24% cubic

More walls and infill is better in this situation, but to print 4 parts with these settings full spool of PETG was needed. I used cheap elegoo rapid petg to print it faster. To attach it to the table up to 16 screws can be used(Screw hole depths are different so check before installing). I also used liquid nails for extra strength. 1 mount has 3 parts so it can be printed on 200 x 200 bed. Parts 1 and 2 need to be mirrored to get parts for opposite side. If anything fails I will update.