I would not want to buy a tin of heavies just to set my power for comps.
I do think that a chart and scales should be in the chrono tent and I for one would like the Marshall to be loading and shooting.
I have heard about a couple of pellets being squeezed at gps and have nearly failed a test myself, but I would not dream of squeezing to clear an important part of a comp.
If the Marshall does the loading at least he can check the pellet.
I don't see why people run their guns close to the limits,there's no gain IMHO .