Yeah, the idea is with aluminum you can double the chip load - no problem, but recutting and welding is a problem when slotting. So you use a 2 flute. Actually, I think most shops these days use a 3 flute for slotting because with modern cutter geometry it works as well as the old two flutes, it is stiffer, and you can feed 50% faster.
If you're doing much of these you should use an endmill with aluminum specific geometry. I love the OSG blizzards for aluminum. Great finishes and chips pouring out of the slot like water out of a hose. But I use the MSC aluminum Accupro because they're cheap, and they go on sale 30% about once a week (just check the website in the morning) and they work well. Look at this one:
http://www1.mscdirect.com/CGI/NNSRI...id=13665Pstoreid=1040626Ppagenumber=593Pmode=
BTW, the ZrN coating is the tits if you ever want to machine copper. Now
that is gummy.
In high productivity machining, but on a Bridgeport (do you have coolant?) I'd slot aluminum with a 1/2" three flute aluminum geometry endmill, perhaps in top gear 2720 RPM, lock the Y axis then feed it at 30-40 IPM. The depth of cut will be a function of spindle HP and rigidity, try 1/8" to start. If you're not using coolant try WD40 (one thing it is good for is machining aluminum).
BTW, I regularly turn that exact cutter at 6000 RPM in aluminum, but on a heavy mill.