Slotting aluminum with small (sub 5mm) tools

[Voicecoil]

Do you mean trochoidal cutting m_c? It does help with chip clearance in my experience, though because of the extra movement I've not found it gives a great improvement in overall speed. Offset overlapping toolpaths can also help, I sometimes use those when deep slotting.

[m_c]

Do you mean trochoidal cutting m_c? It does help with chip clearance in my experience, though because of the extra movement I've not found it gives a great improvement in overall speed. Offset overlapping toolpaths can also help, I sometimes use those when deep slotting.

That's the one.
I almost said Polygonal in my original post, but that's what my lathe does.

On the rare occasion I need to slot something on the mill, I've used a mix of techniques.
Generally once you go deeper than 1.5x-2 times diameter, basic slotting is a risk, more so if you don't have good coolant to flush chips out.
It's worth running various options through your CAM and comparing times.

Trochoidal/Adaptive might appear slower, but since it uses a lot more cutter depth, it can be quicker than multiple passes.
Offset slotting is also worth a try.

It's a case of experimenting to see what works best on the parts you're doing, and with your machine.
A super rigid flex/backlash free machine with through cooolant might be able to rip through slots at 2-3D, but something with a bit flex/backlash and minimal coolant is likely to struggle.