Summary

The current margin setting, 0.05=5%, reserves 19% of the plotting area as additional margin and hence blank (wasted) space. A margin of 0.01=1% reserves/wastes only 4% and would be a better default.

Proposed fix

The default setting should be amended to 0.01 which would add 18.6% usable area.

The amount of wasted space is surprising, given the margin is only 5%. However, we have 4 margins, hence we should expect to waste roughly 4x5% = 20%. More precisely, the plotting area fraction computes to (1 - 2 * 0.05)**2 = 0.81 of the original area.

A margin of 1% is probably what the default margin setting actually intended, as this removes 4% of the usable area (1 - 2 * 0.01)**2 = 0.96.

Changing the margin from 5% to 1% adds 18.6% to the plotting area ((1 - 2 * 0.01)**2 / (1 - 2 * 0.05)**2 = 1.186), or, the other way around, it makes the plot content 18.6% larger without changing the overall plot size.