J, I've only ever grown about 10 different winter squash (including pumpkins) and, as you know, would always defer to your experience! But I have noticed some are more likely to do this than others, and yes, every time it comes down to the weight of the fruit pushing down on itself... I think what I mean is that some are more likely to avoid this on their own - either if they're lighter, or trail more (and in my case, land up on weeds!)...