my experience this summer on 1/c aviation cruise (which was my first experience w/ any real G-forces) may validify the original statement. I'm 5'10" (and around 165 lbs) so I was shorter than about 70-80% of the other mids who were flying. None of us had any prior experience and therefore had no developed G-tolerance. I heard a lot of stories from mids who experienced tunnel-vision and even a couple of instances of grey-out at loads above 6 G. For the most part these were extended pulls (which I would define as more than 1-2 seconds). I noticed that out of all of us, the 4 guys who had these symptoms were also the tallest guys in our group (with the exception of one guy who was about average height comparatively). My personal experience was that I never once felt any sort of greying out. Even on 7+ G pulls (including one 7.4G extended pull-out), I felt pain and struggled to move, but still never got tunnel vision or anything like that. It could be that I was just too pre-occupied to notice that I was greying out, but I think the most likely explantion could be that being shorter helps.
The other question I have is about diet and exercise. Before I went flying I always made sure to hydrate and eat a good meal (mostly so that I wouldn't get sick). Also, I was doing pretty serious push-up and sit-up sets each morning and night and lifting on my off-days (working up for the fall PRT). Could these factors also have helped me w/ G-forces in the jet?