I just ran a quick sim on OT2 and the number looks about right. I got 256 fps and I know that the program always seems high by 10 fps until you adjust the IBO for an arrow shot out of the bow.

Here's something though that seems off. The FOC I'm getting for the 65/80 is 10.43. With the 55/70 it's 11.42%.

I also found that your true IBO is more like 292 for your draw length.

The 65/80's are very overspined for your set-up. However, if the arrow is shooting well don't worry about it. Going to the 125 gr tips would help that out a little and your speed would only drop to about 243 fps.

Your other option would be to go to 55/70'd and shorten the arrow to about 27.5" and you'd be slightly overspined.