When in doubt use the primer, it is magical in terms of making things stick really well!  It is also easy to use. 

How to:
To apply, make sure the surface is fully prepped and dry using the instructions included with the mount.  To use the primer, just push the dot on the side of the stick to start the flow of primer to the application brush tip.  Apply it to the surface in a thin even coat.  Make sure you allow it to dry before installing the FoilMount which is usually 5 minutes at room temperature. 

More Specific Information:
In the back of the FoilMount installation guide; and below, there is a list of the materials the FoilMount will stick the best to and a list of other poor/fair adhesion materials.  You can use the primer to improve the adhesion of these poor/fair adhesion materials so you can still use the FoilMount.  Polyethylene and polypropylene are a few of these materials and can be common on wakeboard and kiteboard bottom surfaces.  If you're using a FoilMount with a board that has a bottom made from a material on the fair adhesion list make sure to use this 3M primer to prepare the surface prior to sticking down the FoilMount. 

This adhesion promoter can be used in a wide variety of applications. It is developed to be used in conjunction with 3M VHB tapes to increase the bonding strength of the tape. It is a popular tool to assist in applying automotive vinyl wraps. It increases the bond between vinyl wraps and nearly anything where a strong, durable bond is required. This product can be used to promote adhesion of 3M tapes to surfaces such polyethylene, polypropylene, ABS, PET/PBT blends, concrete, wood, glass, metal and painted metal surfaces.

List of Materials and Bond Strength:

*Using 3M 94 Tape Primer with these materials should improve bond strength to be acceptable