Last year I replaced my original Amel supplied SSB antenna because the lower section had a crack along it's entire length and the plastic ball mount had broken and been repaired with structural adhesive twice (aging plastic).  My replacement was a Shakespeare SSB antenna with a 1 inch 14-thread per inch female mount on the bottom.  I purchased one of these:    http://shakespeare-ce.com/marine/product/410-r-swivel-mount-mounting-kit/   to mount it but I didn't want to drill holes in the deck to match the mounting plate.  I disassembled the above kit, drilled a slightly larger hole in the existing Amel rectangular aluminum base mount and assembled the SS 1 inch 14-thread per inch swivel onto the aluminum base using nylon isolation washers to prevent dissimilar metal corrosion.  It is way stronger than the original, isn't plastic so it won't age in that way, and I didn't have to drill new holes in the deck.  The antenna also mounts and dismounts (just unscrews) much more easily as I take the antenna down to stow below decks while on the hard for hurricane season. 

All the best, 

Gary Silver

s/v Liahona   on the Hard in Puerto Del Rey, Puerto Rico 

Amel SM #335