Conversion Comparisons

// Original Design

Volume gallonsLeft = Volume.Gallons(1.0f);
gallonsLeft += 1.0f;                        // 2 gallons
gallonsLeft += Volume.Ounces(64.0f);                // 2.5 gallons
Volume litersLeft = gallonsLeft.inLiters;           // 9.46 liters

MethodThatExpectsFloat(gallonsLeft);                // Gets 2.5 gallons
MethodThatExpectsLiters(litersLeft);                // Gets 9.46 liters

// Suggested Design

Volume volumeLeft = 1f * Volume.Gallon;
volumeLeft += 1f * Volume.Gallon;       // 2 gallons
volumeLeft += 64f * Volume.Ounce;       // 2.5 gallons
volumeLeft -= 500f * Volume.Milliliter;     // 2.37 gallons

float gallonsLeft = volumeLeft / Volume.Gallon;
float litersLeft = volumeLeft / Volume.Liter;

MethodThatExpectsFloat(gallonsLeft);        // 2.37 gallons
MethodThatExpectsFloat(litersLeft);     // 8.97143 liters

// Hybrid Design

Volume gallonsLeft = 1f * Volume.Gallon;    // Volume.Gallon keeps gallons as its 'native' unit; this is inherited by gallonsLeft. The actual stored value is still in the common unit, liters.
gallonsLeft += 1f;              // 2 gallons
gallonsLeft += 64f * Volume.Ounce;      // 2.5 gallons
gallonsLeft -= 500f * Volume.Milliliter     // 2.37 gallons
Volume dramsLeft = gallonsLeft.inDrams      // 'Native' unit is drams, as there's an explicit instead of implicit conversion here.

MethodThatExpectsFloat(gallonsLeft);        // Gets 2.37
MethodThatExpectsFloat(dramsLeft);      // Gets 2424.74; internally both gallonsLeft and dramsLeft store the same value: 8.96 (liters).