I wouldn't recommend the U-Can-do as a second pane.

First off, it has some huge control surface and is very responsive with a fast roll rate. This isn't what you want in plane number two. It will be a huge jump going from a trainer to this. You could minimize the throws to deal with this but only to a point. It's best to get something else.

Secondly, the U-Can-Do is prone to aileron flutter. You really have to manage the throttle. This isn;t something you want to have to deal with fresh off of a trainer.

I strongly recommend sticking with one of the more traditional "second planes". There is a good list here: http://www.rcuniverse.com/forum/m_4537845/tm.htm

3-D aerobatics are cool but I'd learn more of the standard aerobatics and flight techniques first. This will make you a better all around pilot. Then when you are ready to give 3-D a try take a look at something like the OMP Edge-540 profile, Mojo, or something similar. These perform 3-D maneuvers better than just about anything out there and are great for learning.

As for proficiency on the simulator... they are great tools but not really equivalent to the real thing. A lot of people can get overly confident from their simulator experience and struggle in real life. I should know because I've fallen into that trap myself.