As blunder pointed out, hypersonic velocities are not necessary to kill with HS. However, I have found that extra velocity can be helpful in opening up the pattern. Some of the best patterns I've achieved with HS loads were with Cabela's 1-1/8oz 1575 fps screamer out of a Terror choke. It would open up to over 30" at 30 yards yet hold killing densities out past 50 yards. On the flip side, I had severe trouble producing consistent, open patterns with slower loads.
I would suggest pattern testing HS before using it. It reacts to choke differently than anything else out there. The blind is not the place to discover your gun/choke/ammo combo is not up to snuff.