p.s Flysurfer, you don't PULL negative g, you PUSH negative g. You PULL positive g. And there are risks in PUSHING negative g in that you can burst blood vessels in your eyeballs if you exceed your tolerance and/or are unlucky. Most people find negative 'g' extremely uncomfortable and you have a lower tolerance for them than positive g. During -g you can reach a state called 'red out'.
+g has stages in the following order: grey out, black out, A-LOC (LOC = Loss Of Conciousness).
The amount of g you can handle depends on a few factors: Size and body type, physical/health state. There is a technique to help from losing conciousness and also the body becomes more tolerant with more exposure to 'g'. The length of time in the 'arc' as 'g' is an acceleration force. The longer you spend in the arc, the more likely you are to lose consciousness even though you might not upon reaching a greater g force if only for a split second or two.
Females of a short and solid build have the greatest natural tolerance for the effects of 'g'. Tall, lean guys like myself have a lower natural tolerance. Bummer, as I love aerobatics when I can afford to do them (General Aviation doesn't pay as well as I wished). I have to work harder at tensing muscles, etc in delaying the loss or gain of blood from head, etc.
Anyway... I have waffled on enough and possibly bored you to tears by now, but hopefully you have learnt something for today.
In the meantime you can experience negative g by accelarating skywards whilst hanging upside down from the bottom of your kite lines.