Yes & No

You may be right, for a space filling model, perhaps one should judge it by volume.

Consider a 50% model of a 10x10x10 cube (very exciting, I know), with a total volume of 1000 units.

If you go by length, then the resulting 50% model would result in a 5x5x5 cube, with a total volume of 125 units, or 1/8 of the above, or (˝×˝×˝).

If you tried to make it half the volume, then the length of side would be [tex]\sqrt[3]{\frac{1}{2}}[/tex] x L

Or, about 0.7937 x L, or nearly 80% of the original length.

So, setting three proportional cars next to each other. The one that is 50% of the volume would be 80% of the length of the original. The one that is 50% of the length of the original would be only about 12.5% of the original volume.

Which is best?

Apparently it gets much more complicated when making model aircraft, because lift is a function of Wing area (square), Cord Length (linear), and Velocity (Should velocity be reduced?).

Volume, and in many senses, mass, of course, is a cubic measurement.

Is drag proportional to the fontal area (a square)?

Anyway, to calculate the aerodynamics of the scale model, you have to incorporate linear measurements, square measurements, and cubic measurements.

Large ships, of course, have a "hull speed" which is a linear measurement. Yet displacement, and most other quantities are cubics.