Glad it helped.

3mm bit was carbide 2 flute slot drill from 'bargain tooling' on e-bay:
3MM CARBIDE SLOT DRILL / CUTTER 2 FLUTE *NEW* | eBay

I don't usually cut much aluminium, so am not an expert, but I have been cutting a fair bit recently for the upgrade parts. The setup I'm using is as below. This is what works on my machine, but no guarantee for yours:

e-bay again from bargain tooling. Can't find link to original part I bought but similar to this:
6MM CARBIDE SLOT DRILL / CUTTER 2 FLUTE *NEW* | eBay
dia: 6mm
material: carbide
flutes: 2

feedrate: 800mm/min
(it feels like it could take 900-1000mm/min which is a better load, but running on 26V machine concerned about stalling/missing steps. Still waiting for new drivers . . . )

plunge rate: 150mm/min

DOC: 1mm
(tried 1.5mm today and tends to squeal / resonate - upgrade parts should improve things)

WOC: 6mm

spindle speed: 12000rpm