Any tips for deep slots/profiling in aluminium?

[JAZZCNC]

Yes but I didn't know if they were up or down spirals or both ?

Well technicly it's possible but you buy Left handed flute tooling and run the spindle in reverse which as the same affect as down cutting or for special cutting conditions where only one direction can be used that would say normally only allow conventional cutting but you want climb mill finish.! or vise versa.
The norm tends to be mostly up cutting with milling tools as like you say breakout is not a problem and everything is usually clamped down tight. You can get them for Composite materials like Carbon fibre and they do Unequal Helix and rougher/finish in one tool etc but they tend to be expensive and often PCD tooling(diamonds). But for general milling and Aluminium then mostly just right handed spiral flute with helix angle to suit material.