Pretty sure there is no fiber underneath. I pulled a set out in 1971, and don't believe there was any of the jute type fiber under those mats. The jute fiber may permeat those mats over time, especially if the car is outdoors in hot climate.
Now, really dumb question. I haven't taken the protective backing off yet, but it appears that the one in the driver's footwell will cover one of the holes for the dimmer switch. Was the switch installed first, then the mat layed over that one hole?
Yeay, I know. Roy Sinor and I were talking and he told me it sounds like my car is "possesing". Play on word instead of progressing.
Thanks again for any help.