Those arrows are weak,way weak according to the archery program. Like at the very end of the spectrum on the scale. 85 grn tips and 50 lbs of draw weight would put them at the right spine for that bow and draw length. If you wanted to stick with the epics, the 340 would be a better choice, the 400 if you droped to 60 lbs. The 340's would be 396 grns though with a 10% foc.

I was looking to see if something that would spine well would come up at the same weight or not, no luck so far, at least at that length and a 100 grn tip. Most are a little heavier or lighter. I don't know if I would suggest going much lighter. I will play a little more with different tip weights and see what I come up with. I assume you are using vanes, probably 3 inches by the overall weight of your arrow.

With the Parker Feather MagII it shows these arrows with a 100 grn tip and 61 lbs of draw barely in the green, but on the weak side, they are just about perfect with a 85grn tip.

You have to take into account that from bow to bow or manufacturer to manufacturer the cams effeciency changes. The bowtechs have very agressive cams and are very effecient at storing energy. That is why they are so popoular. But it also effects the spine of the arrow. Taking into account the better cam and the increase in draw weight, I am not surprised they are weak, especially when they were on the line to begin with. Actually when you take into account the extra weight on your string like nock, peep, and silencers they were probably dead on with the Parker. When you look at the arrow charts and they ask for cam type and it says wheel, medium, or hard. It should now read, medium, hard or BOWTECH!.

For a comparison, here are the specs for the two bows you comparing.

The parker has a performance factor of 1.1807 and the bowtech is 1.2585, with almost a 20 fps faster IBO rating.

Paul