just a suggestion.
Regulators placed in that way, seem have very little place for dissipate heat.
You already put a thick aluminium part between them for dissipate, but mainly in this position, it equalize the heat on all the chips.
You can improve the dissipation making the aluminium that you use as dissipator in a disk of the exact diameter of the inside regulators boards enclosure, and in the mounting, putting some thermal grease or thermoconductive glue (for a permanent mount), on the chips, assembling them with the aluminium disk, then putting a little thermal grease also on the border of it, when you push it in place, so it can dissipate some temperature on the holder, improving the life of your regulators
As in the draw, i mean, cause with the english i'm not too good
