Hiya, Wide,
Enjoyed meeting you briefly at soggy Sandown the other weekend, pity about the weather. Yes, absolutely, +4 and zero are all I would wish to use in a Chipmunk nowadays, I am older (as are the aeroplanes) and I hope a bit more mechanically sensitive than I was in my early 20s. Even in the Yak I've never exceeded +5 -2, but then I'm not competing in it and I'm only really a Sunday afternoon looper and roller.
Sleeve,
I don't think I'd really want to do aerobatics in anything without a G meter, or indeed fly any aeroplane that was being aerobatted by lots of other people if it didn't have a G meter. And I'd forgotten about the oil dripping all off the lower fuselage, it was even worse than cleaning up the Yak!
Milt,
You make a very good point about the way the stresses build up when G is applied in conjunction with aileron, and one which is not very often considered in operating handbooks in my experience. The troubles of the T-34 fleet in the USA are a case in point. Use of significant aileron must not only be done with consideraton of speed, but also G, and in the absence of any formal G / aileron envelope it is wise to unload, roll and pull in best fighter pilot fashion. For those occasions when one must pull and roll at the same time, I work on the basis of half and half, i.e. maxiumum of half aileron with a maximum of half the G limit. That's plenty to accomodate barrel roll entries and similar manoeuvres.
Jabber,
On everything non-aerobatic I've seen, Normal category is +3.8G, and Utility category is +4.4G, so +3G sounds a bit low for a Semi-aerobatic category. I think anything allowed to do aerobatics at all would have to be placarded at no less than +4.4g.
Gliders might be an exception, though, most of them in my gliding days were placarded at +3.5G, and that seemed to be enough for the occasional loop. Mind you, those were the days when we used to do spin training straight off launch at 1200 feet in the K-13 at North Weald, two turns and into the downwind leg at 600 feet, fair gives me the quivers to think about spinning that low down these days.