After drilling the ends, I would "drill" the center of the slot with a .125 end mill.
Then use plenty of coolant, and cut the profile with the end mill (.060 is a fine depth of cut). If not coolant, plenty of air.
I would relieve the end mill (grind diameter a few thousandths smaller)! If your depth of cut is .06, all you really need as far as flute length is .06 (okay, a bit more than that, but...).
Any extra flute length will likely bind, and cause chatter in the ends of your slot - not to mention if your tool is a bit worn at the cutting end, when the full-size shank reaches the slightly-undersize slot, it will rub a bit and then break.
Hope this helps!