I have tried Ritrama and KPMF both supplied by MDP supplies. Really great service and the product applies well.
However, the challenge with the stoneguard is its thickness relative to regular colour change films, when applying over double curves ie the rear arches. It is 3 or 4 times thicker, up to 320 micron as opposed to 80-100 micron.
After several attempts, warm, wet, stretched, trimmed; I still had some wrinkles where the film wrapped under the edge of the rear arches.
On the plus side I successfully used these films for the lower edge of the sideskins and in various other paint scuff areas where it is either flat or single curve.
I took my car to a local firm (Race by Design near gatwick airport). They did a supply and fit using 3M ventureshield for the rear arches, £50 a side. The film goes right up to where the sidescreen ends. Even they had a problem with a couple of areas of wrinkling, but removed and replaced using an updated template free of charge. Guy is the main man and pleased to recommend them.