Heating of fruit shortened the fruit growth period and reduced final fruit size.
Response of Cell Division and Cell Expansion to Local Fruit Heating in Tomato Fruit
So the take home message to all growers.... Keep your fruit cool and away from direct sunlight after the cell expansion phase ends... Remedy, Cover it or enclose it completely as Chris Delaney did years ago..... Always have a fan blow fresh air over the fruit.... This drives transpiration from the fruit itself..... So it will become a stronger sink as it demands more nutrients from both the xylem & phloem..
Journal of the American Society for Horticultural
JASHS September 2012 vol. 137 no. 5 294-301
"Heated fruit were smaller because their mesocarps were smaller than those of controlled fruit."
Mescarp is the mid outer layer or fleshiest layer of the pumpkin, the yellow, orange-ish walls .
"A multilevel analysis of fruit growth of two tomato cultivars in response to fruit temperature"
Physiologia Plantarum Volume 153, Issue 3, pages 403–418, March 2015