If you're using the standard plastic fog lamps be careful what you stick to them, not all adhesives are plastic friendly. Best thing to do is get the sheet stuff from Griots, pull the light out of the car and make your own, as long as theirs is safe on that material.....I'd put an upgraded light in there myself.....
Been using the clear adhesive for years (on lower lights/fogs), and while it won't protect from a major impact, it protects daily from the other 99% of 'stuff' that hits them. I don't have the SVTC (all my other cars have lights, and more lights....all glass) but my SVTF has the 4" glass Valeo's (bigger target than yours) and now I've made and installed covers over the entire opening. The adhesive was good it's just that the Valeo lens is very slightly curved and the adhesive lifts around the edges giving a real UNattractive dirt halo effect, arrrggggg. Not sure if anyone ever tried a DIY fog cover on the SVTC though. This is only time I've seen them on the SVTF.
The big rectangular ones have the thick adhesive on them and have for, well, years. I have some marks in the adhesive but no breaks yet and I do 47 mi one way to work, and uncover the lights every morning for the dark trip home. Trust me, where those are mounted, they get quite a beating.
BTW, the REALLY nice glass Cibie 3" from the Marauders work pretty well in the SVTC (my son, 'can't drive 55' has them in his SVTC) if you ever get tired of the ineffective plastic throw away stock units, the Cibie's WORK really nice......those stock units are embarassing......their range can be measured with a tape measure right?

What do they cost new, like 10 bucks or something?