Just for laughs I decided to try a proper barrel roll today, inbetween the practice for the UK Standard 2009 sequence. So roll rate constant, g force constant, level in both axis over the top and no height loss. Took me three tries before I could pull it off again.
Of course this was in an aerobatics aircraft with plenty height and everything. But I was still surprised about how hard it is, especially after not having done one for a year or so. And I'm not exactly rusty when it comes to aerobatics.