Rocket used to have speed ratings for their heads on their web site. I guess they figure a certain FPS carries a certain KE adequate to get the job done. However, they've apparently not included this info in their new site.

From memory, I think the fps rating was pretty low for the 1.5" heads, like 240ish.

I personally don't think 1.5" cut at 60'#s of ke is a problem, especially after I sharpen them up