Re: wet canvas box for 3/4 in ampersand cradled boards?
Not sure if this will work for you but hope it will. Handy Porter boxes from Guerilla Painter can accommodate two 3/4 inch canvases or 4 panels. These boxes are cardboard with polystyrene (Styrofoam) molded inserts that hold the canvases/panels. I reinforce the handles with tongue depressor/popsicle sticks and duct tape. The largest size is 12x16. The 12x16 is around $10 from Jerrys Artarama or a comparable venue. i use them regularly to transport canvases. Two 12x16s strapped together count as one carry on and fis in the overhead luggage compartment.
C&C Always Welcome