Interesting idea, though I wouldn't use them for anything but light riding (dual sport, nothing serious) as I have a feeling they'll slip in the clamps. I also think there will be alignment issues after a crash. Cool idea though.
I have the 2 inch version of that five inch one in the pic on my sled. These are stout units. If you break one of these your gonna have a whole lot of other broken stuff on your bike and body. I Suppose slippage could be a concern but these are very popular on sleds, have been around for years and I haven't had nor heard of Any slippage issues. Steering components on snowmobiles get a ton more stress than anything on a bike. If i needed a 2" rise on my bike i'd swap over the ones I have. However my bars are fine the way they are.