After thoroughly reading this case and clarifying claims about the boundary in-game, I've made a decision.
LavaFlake attempted to region trump15024 a very large plot, probably more than what was necessary. To clarify, plots don't have to be a square or rectangle to region, it's just more convenient. But anyways, trump15024, you had no right to extend the boundary after the regioning request was made. Instead, you could've contacted LavaFlake or nibble to postpone the regioning so you could ask him about making the plot into a square/rectangle.
I've read that both parties involved said that trump15024 extended the plot boundary by 50 blocks. Since trump15024 could have easily contacted LavaFlake or nibble to put the regioning request on hold to figure out the "shape problem," I believe that he is in the wrong here. Also, both players involved agreed on the size of the boundary expansion.
Since trump15024 expanded the boundary by 50 blocks, I think it's only fair to have his new plot be decreased in size by 50 blocks on the same side that he extended.
Case closed.