Heinz, the size of the gap and location will dictate whether I use superglue or putty. More often than not I tend to use superglue but it can sometimes be a pain in fiddly areas, such as the base of the fin where there can be some delicate detail. I try to work very carefully to avoid losing panel line detail, putty is better to use in these areas as it is much easier to rescribe detail if some still remains, the putty is softer than the superglue.