You might actually want to transition from double-thick to single-thick,and taper
strongly for an axe-shape. Think Aerodyne, but moreso.
(I cannot seem to find a decent end-on view of a double-bit axe, but you get the idea from that picture, I think - though structural concerns will keep you from going that far on a wooden build.)
You might also want to put some heavy metal (lead, barring handy sources of scrap tungsten) on/in the bridge-end WRT neckdive (since you can't futz with the strap locations and stay true to character, weight distribution is your friend) and/or contour so that the bridge-side of the axe-blade is thicker than the neck side (ie, make neck to blade-edge taper, but also make the taper fatter at the bridge end and skinnier at the neck end. Given you'll paint it, any pine/basswood in the scrap bin? you could mahoganize (IIRC what you bought at the start of the thread) the bridge and transition to pine/bass towards the neck on the blades/wings.
Also (if you get ambitious) might want to see if you can rig some sort of un-strap (back swiveling connection to a belt, maybe?) since she often seems to float with it and play without a strap...