I've recently modified my old Hero3 with a "Back-Bone" mod kit, It's call the "Ribcage" and sells for around $250. What it allows you to do is run just about any lens you can find on the your GoPro, You do lose the ability to use the waterproof housing but it does give you some awesome benefits when it come to being creative. The kit comes with everything you need to do the mod and they have video and pfd documents on their website that walk you through the process step by step, It's relatively easy but take you time. The bits are mostly machined out of metal but there are the odd plastic bits but they all seem top quality. Out of the box you can run any C-mount or m12 lenses but there are numerous adapters available to suit most lenses. I got myself a Canon EF adapter with iris control so I can use my current batch of lenses I own from my DSLR. I shot a little bit of video yesterday just to see what it does, I like what I've seen so far and think it's got potential to get some really good footage. More experimentation to come though, I'm going to see what 720@120fps can capture.

Anyways take a look and see what you think....