The 2.5” drives mount slightly off center on the drive plates. This is so the data and power line up correctly.
The 3.5” drives mount from the bottom, and fill up the drive plate nicely. There’s room for three (3) drives.
With an SSD (top) and an HDD (bottom) mounted in two (2) of the drive trays, you can see how the power/data connectors line up nicely with holes cut out for the cables.
There are an additional two (2) sets of holes drilled for mounting a 2.5” drive on the motherboard tray.
The two (2) 120mm fans mount tightly in the fan bracket with screws from the bottom.
One problem to note, the motherboard tray 2.5” drive mounting may have clearance issues with some radiators (XSPC AX240 shown, 40mm thick). It hits the SSD, which could be avoided if the fan bracket had an offset from the motherboard tray (of as little as 3-4mm). A thinner radiator would not be an issue.
There is about 4-3/8” space between the motherboard and the fan bracket.
A GPU up to 340mm can be mounted in the D-Frame Mini.
There’s about 3/4″ between the GPU and the fan shroud. This is something that may determine radiator orientation, if you plan to water cool.