I seem to recall threads mentioning carpet samples applied to boards to bridge between two or more crossmembers. Applied how? You wouldn't want any nail or staple to be near the carpet surface. Construction adhesive sounds better. How elaborate depends on your intentions.
Make sure any padding you use is new, has no grit, etc. You wouldn't want to scratch your nice clearcoat! Set it in place; don't slide.
Means of making it secure enough for safety are entirely up to you. Eight feet up is enough to cause some serious damage.
Mustn't be snowing in Montreal like it is here. Watch out -- it's coming your way.
The other guys gave you good advice..One additional thing to remember: Whatever you do, Do Not try to access the top area from the end caps~! Either the front or rear..It much safer to tackle the roof top by the area in the middle..
__________________ WBCCI 5292 AIR 807 NEU #64 New England Unit