Keep the cage in a horizontal orientation....boas are pretty terrestrial as they get bigger. You should have an area with exposure to sun, but also a shaded area where they can escape exposure....maybe 1/2 exposed and 1/2 shaded. I usually feed boas in the evening, but I've found they'll eat pretty much any time of day. If you have trouble feeding try early evening or early morning. Rabbits are probably the only animal you can leave live in cage and not have to worry about them injuring the snake(rats, mice, etc. would end up chewing on the snake). If they snake doesn't eat within 1/2 hour though, take the rabbit out. I would make the bottom plywood. Wire mesh may cause abrasions on the snake. Even with straw, the snake may end up pushing it away and laying on exposed wire.