Gourds are just awesome aren't they? One of my best ukuleles was a gourd and i'm still trying to find some in my area that haven't been turned into birdhouses yet... :D
That sure is pretty.I think any mistakes you might have made can't be seen here.Thank you for showing it to me.
AS long as you stick with the 'Stick-thru' style, I don't foresee much of a problem. I've done plenty of double-course, even a full Mandolin on a tennis racquet (to be fair however a racquet has plenty of sturdy laminations built in!).
If you're worried about strength, I would simply recommend a vertically-laminated stick under your fretboard for extra resistance to deformation, and (possibly) a slim reinforcing rib under your soundboard for any extra Bridge pressure-and at that, you might be overbuilding...
A friend of mine made one back in the 90's. His was a double neck, 1 was tuned to G and the other tuned to D so he didn't have to change tuning or instruments between songs.
I made one shortly afterward(my first attempt at making an instrument) which wasn't great looking. Couple of years ago I made a 6 string baritone 28" scale dulcimer/dulcitar neck and put it on a Squier Affinity Strat. There's a pic in my photos.
Hope you enjoy yours as much as I enjoy mine.