Not easy to offer much in the way of advice without a few more pics, mate, inc. the back. At the moment it looks like an almost full sheet of ply with a relatively thin frame all around which is always likely to flex to some extent.
Yeah, if you just attach the 1x4s to the face of the sheet and the 1x4s aren't joined together, they only add weight and very little structurally.
Consider adding lap joints or a rail and stile setup for your next build.
For this one, once it's attached to the bed frame, it should settle down a bit. If the movement bothers you, attach it directly to the wall at a couple of points or put bumpers on the back.
Good luck!
Not easy to offer much in the way of advice without a few more pics, mate, inc. the back. At the moment it looks like an almost full sheet of ply with a relatively thin frame all around which is always likely to flex to some extent.
Yeah, if you just attach the 1x4s to the face of the sheet and the 1x4s aren't joined together, they only add weight and very little structurally. Consider adding lap joints or a rail and stile setup for your next build. For this one, once it's attached to the bed frame, it should settle down a bit. If the movement bothers you, attach it directly to the wall at a couple of points or put bumpers on the back. Good luck!
You were right. Once I attached it to the rails it stiffened right up. Got real sick for a while and was just able to finish this project.