I just bought the 3DS XL last weekend alongwith MH3U, and since I didn't have the money to purchase the Circle Pad Pro at the time, I just played MH3U as is.
It wasn't as bad as I anticipated to be. While my hands did cramp up because I was not used to holding the 3DS XL, the controls/interface were made much easier by the move-able panels on the touch screen. Just put the camera control in the top right corner, make that sucker as large as possible, and I was able to play as as if I had two thumb sticks. The lock on feature hels a whole lot, especially under water which is takes the most time getting used to.
Anyone that thinks it is impossible to play well without it, you shouldn't be worried unless you somehow suck with touchscreens.
It would probably be easier with the CPP, since it would provide better grip and additional shoulder buttons, but I will have to decide whether I want another game or the CPP.
If any cares to help me, Is the CPP worth it?
If I find someone on street pass is it possible to send them a message or add them to my friend list?