I, personally, would change the rules there a bit.
1) This is the hardest part; do a good job or none of the rest will work right
2) Do not use a one piece sleeve for that mast, that would be waste of time and money, and it won’t work well, use two pieces to do just the sides, maybe one more for the front panel, but not absolutely needed - the sleeves will be 3X mast fore/aft chord - on your stick this is 24"
3) Also make a taper to the splice, i.e. the back edge of the splice will be longer than the front edge by 4" or more -
4) Your first set of holes will be 4 fastener diameters from the joint, and then you will set up a staggered pattern at 8d apart until you have used up the whole sleeve of fastening area
5) Use 1/4"-20 FHMS undercut heads 1/2" long - if you use normal heads you will just bottom out on the plates before achieving clamping pressure
6) Use Life Seal to seal threads, if you really care use Hysol 9342 (or similar) to bond the plates to the mast wall - this is a waste of time unless you prep the inside of the mast for adhesion! Anyway, not needed and most masts go together 'dry' except for something on the screws.
Oh, and of course - this job should only be completed by an experienced rigger after consulting with a naval architect, a yacht surveyor, and the insurance carrier for the yachts' coverage
