Just build it the way the plans say and it'll be fine.
I've been flying one for about 5 years now and I love it.
Does spectacular aeobatics, especially snaps and lomcivoks(sp)
The extra weight seems to increase it's ability to tumble end over end.
I have a YS 120 in mine, which is a fairly heavy engine, and it balanced fine with no added weight.

Also, it lands very slow if you want. No bad habits.