3M Diamond Grade prismatic film (otherwise known as Railroad spec reflective film, or
SOLAS spec film) reflects significantly more light than the 680 spec film, but it is very difficult to work with unless you are applying it to a perfectly flat surface (for example, the side of a railway locomotive).
It is a very thick film that does not respond well to any attempts to heat it to make it conform to a surface with compound curves. For that reason, I don't think it is the best choice for our motorcycles unless the rider puts a very high priority on conspicuity, and even then it is only suitable for use on the rear face of ST 1300 saddlebags (it's not suitable for anywhere on the ST 1100). If you elect to use Diamond Grade film, be sure to purchase the 4090 specification, which adheres to plastic, and not the 4080 specification, which is intended for use on aluminum or plywood only.
Michael