Darco fabric torn under slide

[fatcatzzz]

I am having a problem with the Darco fabric being torn when the slide comes in. There are two furnace grills the slide rubs on and is tears the fabric. Slide has been adjusted but still rubs. Poor design! Anyway I am thinking of adding some strips of UHMW 3/16 6×35 plastic to the bottom of the slide so the slide will ride 3/16" higher and clear the grills.

Has anyone done anything like this?
How wide should strip be?
How many stips?
Fasteners?

Thanks in advance for any help.