I did my homework.
According to Clarke, Christopher Frazier actually did a study at two sites using N. rafflesiana, ampullaria and gracilis as the study plants. The two sites had both 'closed' and 'open' microenvironments. In the 'open' areas, 100% of rafflesiana was male, and 83% of gracilis was male. there were no ampullarias growing in the 'open' areas. In the closed areas, females accounted for more than 50 percent of the flowering plants, with the number hovering around 60 percent+. This fits in precisely with Rob's plants grown 'close' and then exposed to 'open', the larger population of females reveal themselves-when stressed. Frazier noted the need for females to expend more energy bearing fruit and seed and would thus require a more nurturing environment. The males could tough it out on the white sand. He also noted that the male flowers in the open were more accessible to potential pollinators-higher visibility, and produced less sugar than the females. He suggests its to get the pollinator to the male flower just long enough to pick up the pollen, and then find the larger quantities of sugar at the female flower, spend more time at the female, assuring pollination.