I agree with the others, and alternative is to find a thick piece of plywood, anchor this up with as many fittings as you can, 1 in each corner 1 on each side and a few in the centre, then attach the hood to this instead. If you can, buy some no nails as well just for added support, this method will spread the load over a greater space and thus decrease pressure on the anchors.
In my opinion you may still be better finding a stud, but in the worst case that will do the job.
Stocky