I have been using Niagara Stabilizer tools on Ti-6-4 and Viscount 44 on a VF5 40T with the same spindle. Depending on how good you need the surface finish, and how good you can hold the part you should be able to get some pretty good material removal rates.
For a 1/4" diameter, they list 350 sfpm and .0009 ipt chipload . They claim 1D slot cutting depth. I have been using very close the listed speeds and feeds at .7D slot depth.
If you can clamp your part to a consumable base plate (aluminum plate), I would get a .250" niagara stabilizer, run it at 5348RPM 18.2 ipm and .13 depth of cut (.13 first pass in material, .095 second pass for breakout)