DIY double bed frame plans?

Hello good folks. I want to build a frame for a double bed in the back of my 31 foot '81 Excella (where there were two single beds I removed). Surely someone has posted plans or tips here but I haven't been able to find them. I have drawn up a sketch with a friend that I feel good about but would much prefer hearing from someone who has already succeeded just to save time. The length of the bed will be oriented parallel to the bumper and I plan on having the mattress cut to be flush with the curve (have to research who makes those). I want to use slats instead of plywood to help with air circulation. I also want to be able to store under the bed (just slide stuff under, nothing fancy). Thanks for any leads!