I hope this is in right section,

Ive orderd a shark fin aerial as the rubber base on my VX one has perished and has come off.
As I panicked and imagined water running in and soaking my headlining I rushed on to ebay and bought one.... I then got the vec out of garage this morning and realised the rear washer is incorparated into the aerial base... my problem is.. can the shark fin be modded..adapted to make the jet piece fit?
Has anyone done this? and could point me in the right direction to a solution.

Otherwise its de-wiper the rear and disconnet the wiper motor and take the fuse out, which I would imagine would stop the rear wash wipe from working aswell.

Any comments or advice would be great.
Cheers in advance.