I would suggest just plain ole hot glue just in case you need to service the board/diode in the future. Getting certain glues off for a repair is rather hard depending on the glue.
Also, lots of Capacitors in PSU's are fixed in place with a white silicone style glue and even that can be a pain to remove but not impossible.
I guess what I am trying to say is that a permanent glue might not be what you want.
Good Luck!