HDPE Help?

I'm working on a project in HDPE. It's .187 thick & I need to cut about 60 full depth pockets in it that measure 1.5 x 1.2. The only bits I have are 1/8" o-flute upcut(Onsrud 65-012) & a 1/2" low helix 2-flute bit for plastics (Vortex 4260). From what I've calculated, if I use the 1/8" bit the machine time is around 7 hours. The 1/2" is around 14 minutes, but at 500IPM. I have an Alpha Buddy, but I've just never cut anything like HDPE, especially that fast. The 1/8" numbers I am using are 60ipm @ 12k rpm & a cut depth of 0.05. The 1/2", I'm using 500IPM @ 9k rpm at 0.1 depth. Any ideas or suggestions?

Thanks
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