diy hawaian sling -question and pics

[AVINOAM]

hi,
i have build this sling from stainless steel, wood, epooxy and fiberglass.
i hvave made the sling butt (i dont know axactly if thats the part name) from stainlees steell and im concern that it wont knock on my hand while shooting.
i can see that in slings that you can buy the but made also from metal.
is there no danger to the hand/ to the wood from that part or maybe because its underwater and still nedd to push the arrow, the kick is easy?
thanks

sorry for my bed english

 

[AVINOAM]

 

[AVINOAM]

here is a link to a stainless steel sling butt
http://www.spearfishingworld.com/abbiller-hawaiian-sling.html

 

[AVINOAM]

I tried somthing and i hope it will work.
I took rubber of speargun and made this
Inside there is a small plastic ball to prevent the arrow from stuck to dip