I believe that age is more important then size. As long as they're at least three years old they should be OK to handle laying. I've had several females that were less then 900 grams lay perfectly good and healthy clutches. Clutch sizes ARE smaller, but they'll also often lay every year whereas my largest females seem to like to take every other year off.
Perhaps it's just easier for these smaller females to get back up to THEIR perfect weight. (as opposed to the weight that I'D like them to be)