The height of the finial seems rather high but how does it look with the remainder of the cap? If the metal portion fits into the pattern it should look great.
are you going to leave it shaped like it is sitting on there or will youturn it down until it just peeks up over the metal? If you are going to turn it down it will look ok if it matches the rest of the blank.
It looks a little big (high) but maybe when it is installed it will not look to big/high.. Personally, a custom finial on a pen/pencil really makes a difference from a standard kit pen..