Agree. Anything will fit with good adhesion UV resistance and no acid involved. As for hot silicone I noticed that the one I tried is easily detached from the base once hardened.Self-fusing tape is great for connectors and here also could fit but in this particular case I should remove all the black plastic which is not good idea as it is involved in mechanical construction of the antenna. Rather I will use it as base and will fill up with kind of compound, most likely UV resistant polyurethane. Afterwards may insure it with selfamalgamating tape as suggested.
Will share result here.
That actually is one reason I decided aigainstputting it outside, as it meant to place it somewhere I could not easily reach and check if something is wrong due eg water ingress.