I installed a set on a C414A back in the 90's when I was doing A&P stuff. As I recall, they were quite trivial to install as well. I think there was a roll-on paper template with cutouts for the VG's and special glue. Cleaned the surface per recommendation. Rolled on included paper template indexing to specific reference points. Took the VG's out, applied glue, applied and let cure. Then went to test fly..lowered stall by several KTS and also made it handle less mushy. I think even for that aircraft the things only weighed several ounces so added weight was absolutely negligible.