Mizzen Mast Splice

[sdear]

I have an Allied Seawind II ketch. I'm going to add 18" - 24" to the bottom of my mizzen mast so I can stand under the boom without hitting my head or reducing the sails sq. ft.
I've got two 2' sections of the extrusion. 1 for the added length and 1 for the internal splice.
So here's the question. Is it acceptable for the internal splice to be made of 2 seperate pieces that fit along each side but not around the forward or aft ends? These 2 pieces would protrude into the existing mast section 12" and into the new section 12". Or, does the splice need to be a single piece that fits the whole inside perimeter?
Thanks!