From my experience with the Sevr 2.0 and 2.1 on deer, I won't personally use them on Elk. No more cutting area of the 1.5 I'd just shoot a fixed.
The Thorn broadhead has half a blunt on the front, there's no way I'd use them on big game.
I am a fan of the Spitfire, it has just worked really well for me, could be something better, but I haven't used it, and I shoot a lot of different heads. Wouldn't have an issue with a Grim Reaper mech, except their largest cut versions for Elk.
Make sure you aren't using a mech to fix tuning issues, cause you aren't.