Dragon 64:
I was thinking the same as you about the Challenger, mostly because I like the stock.
The GOBs are an awsome group, and really have a lot of good shooters. I know that you will enjoy shooting with them. Listen to what they tell you, because they know.
A word of advise to a new FT shooter, don't be intimidated, and you will not do as good as you know you can the first few times. But you will get better every time you go. I almost gave up on it the third time I shot, I was so frustrated. It seemed I did every rookie mistake that you could do. Everything from dropping my gun to forgetting to lock down my scope adjustments. Last month I forgot my pellets and magazines, I had to readjust my scope with a different kind of pellets, 20 minutes before the match started. My scores starting from the first time I went = 14, 19, 16, 30, 36 last month, Dec. I'm shooting for 42-48 which will put me in mid pack.
If you hang in there, you will really enjoy it and become addicted to it as I have.
The Mrod is an excellent gun for FT. It just needs to be tweaked.