Fun fact the PCB inside the SSD's case is pretty small and in most cases can be removed and run without the unneeded metal bits. I don't think they even need the 2.5 size case as a thermal solution. (though one could argue the 3.5 drive would make a much better heatsink then the original case if you can thermally connect the board to the 3.5 drive). It might have been easier to just take it out and mount in place of the original PCB on the 3.5 drive. Though you might still need to tap new screw holes and perhaps add some insulation between the board and the hard-drive case. EDIT: Unless you meant to make this as a usable adapter housing for any 2.5 SSD you come across and isn't dedicated to that one SSD you put in it. Then my idea wouldn't be as convenient in that case.
Fun fact the PCB inside the SSD's case is pretty small and in most cases can be removed and run without the unneeded metal bits. I don't think they even need the 2.5 size case as a thermal solution. (though one could argue the 3.5 drive would make a much better heatsink then the original case if you can thermally connect the board to the 3.5 drive).
It might have been easier to just take it out and mount in place of the original PCB on the 3.5 drive. Though you might still need to tap new screw holes and perhaps add some insulation between the board and the hard-drive case.
EDIT:
Unless you meant to make this as a usable adapter housing for any 2.5 SSD you come across and isn't dedicated to that one SSD you put in it. Then my idea wouldn't be as convenient in that case.