You will need a double fish tail splice. I have no build along that I have done, but I have spliced may billets together. My favorite and most easy splice is the scarf joint, but you dont have the material for that. Each limb needs to be cut to the shape of the female end of the fish tail splice, then make a double male joint to fill in the area between the two females.
I have done this on tip levers before. Ensure the best glue lines you can get, and fill any voids with glue sawdust mix. Go heavy on the glue in the mix. After that has dried a day, laminate on your belly handle riser, then for good measure ( though probably not needed ) a thin riser on the back as well. Once dry for 24 hours minimum ( assuming you use TBIII ) shape the handle and stress the joint. My money is on your handle will never break again.
Like I said, I have done this on tip leavers in the past and they hold just fine. Will try to find some pics of it. But look up fish tail splices to see what I mean, and make them as long as you can to get the most surface area glued up as possible. You want a minimum of 8 to 1 length to thickness ratio of contact surface area in your splice.