-
Also @tbc
If the decor panels are 18mm mdf I’m pretty sure they’d support shelf pins.
Most likely 15mm/18mm chipboard (depending on manufacturer) but will still hold it.
I'm with trunkie on this, if the shelf fits the space well then all of the weight will be transmitted down through the decor panel if you put a screw or shelf pin there it will not pull away. By using the tracks you are overcomplicating things significantly and making the space less usable as well.
If you use a twin slot system wont you need to rebate them in the decor panel? Otherwise you’ll need to have the shelves notched, or cut shorter than the width of the opening, which will look weird.
If the decor panels are 18mm mdf I’m pretty sure they’d support shelf pins. I’ve used them on alcove shelves about triple the width you’re looking at with no issues.
Another option could be to use worktop offcuts along the back of the recess between the shelves as extra support. This would mean they wouldn’t be adjustable though of course.