Nice target chassis choice!
Really, I like that box a lot. Glad to see designed for AC from the ground up ('specially with MOSFETs).
I'm in full support of more board-mounted options, such as nested pads for the DaCT attenuator and Alps, plus on-board fusing as an option that can be jumpered if rear-panel access is preferred.
Glad you are planning to drive the MOSFETs directly from the OPAs... I like that.
When will the boards be ready? (kidding- no reply requested!)