There are studies. Hence the multiple cheating scandals, because we know how small of a change can massively affect your flight. Here’s one:

https://pmc.ncbi.nlm.nih.gov/articles/PMC12611860/

Changing the suit circumference by +2 cm increased the lift area (𝐶𝑙⁢𝐴) by ∼5% and the drag area (𝐶𝑑⁢𝐴) by ∼4%. This was simulated to change the jump length by 5.8 m, which corresponds to an increase of 2.8 m/cm in suit tolerance, for a reference jump of 130 m

2.8 meters for every increase in a single centimeter of circumference.