This one will be around for a while... heavy as sin, but solid.
Used 11 2x2 removable slats per level spaced 5 1/2" apart by 2x2s.
Added a 44" ladder and back rail and front rail with 30 degree miter cut on 2x4s.
Next time, would have sanded & stained the headboard/footboard 2x6s on the ends before screwing them to 2x4s. Didn't have a sander that could get between the 1/2" gap and the hand sanding from position can be tough. Overall, very pleased with the result.
Kids love it! First of many projects I will be doing from this website.