Bigbulls, the shockwaves are an excellent mechanical head for deer, but as you found out not for elk. Elk are just so much bigger and tougher than deer. Most mechanical heads are made with deer hunters in mind.
The monotec's are plenty strong. The phantoms and bear razorheads are also very strong heads, and should be able to withstand a heavy bone. The steelforce heads are going to be the least strong, most becuase of the large unsupported tip. That is not to say they are not strong heads, they are, but from my testing they would be the first ones to bend on identical hits.
You may also want to consider some of the Magnus heads. The snuffers are similer to the monotecs, only bigger, and not quite as strong overall. Magnus also makes a bunch of two and 4 blade heads. The Stingers are a more modern style with stainless blades and come razor sharp out of the package.
Keep in mind though "heavy" bone is a pretty broad term. Ribs, and spine are one thing. a big heavy shouler or leg bone is another. I don't think any head will penetrate really heavy bones unless you have some serieous Kinetic energy. To be honest though any of the heads you listed would be a good choice, and much much better than the shockwaves for elk.

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