It's hard to convey emotion on the internet, so don't take this the wrong way. But I just don't see the use of doing something like cross fit, which to me is way more risky than traditional training, for 4 weeks. Doing fast and volumized work to me is more of a way of life for crossfitters. I would just just do high volume traditional work, or more dynamic or speed work if you just want a shock. Crossfit can have you throwing alot of fundamentals out of the window for a handful of reasons. But if you're just curious or don't give a shit, then have at it. A 4 week stint will provide results that would be of lower value to me. Now GPP stuff is great, but just be careful. Let us know what you do and find out. it would be interesting to see.