I would recommend you keep the flex PSU layout then.
There should be an integrated plugin DC board + meanwell 400W next year. It's on my list of projects. It has a slightly smaller foot print than flex PSU, uses fewer cables, and can be fanless. The model is rps-400-12-c.
There should be an integrated plugin DC board + meanwell 400W next year. It's on my list of projects. It has a slightly smaller foot print than flex PSU, uses fewer cables, and can be fanless. The model is rps-400-12-c.