How are you coming with the challenge and has it helped you?
It has helped me tremendously. I did the challenge with my Sharps rifle because I really wanted to see improvement with something that had some recoil thrown in. Sitting groups off the cross sticks went from about 6 inches (yes, cross sticks take a little learning to shoot well, at least in my case!

The most important thing I have learned is to properly follow through during the recoil. I had a tendancy to lift my head during recoil and I think I have that cured now.
The test will come during deer season this year and Africa in May. It is tougher than one might think to burn that much powder, but it can be done if you want to badly enough.
I'm working on range cards for various 10 yd increments from 100 to 300yds right now.
Please tell us about your progress.