4408 litres of volume for LH2 might seem a killer, but when one considers that the volume of a Continental six cylinder engine (TSIOF-550-D) occupies

http://www.continentalmotors.aero/up...ies_032012.pdf

43 inches x 43 inches x 64 inches - a total volume of 1,940 litres. Adding 410 litres to this volume we have 2,350 litres - more than half the required 4,408 to carry all the hydrogen the weight chart indicated previously.

This volume is just for the engine block as shown. When one counts the 410 litres for the av-gas along with the intake and exhaust volumes in the airframe of the Valkyrie, we can easily find 4,408 litres of hydrogen tank volume along with the volume needed for the compact electric motor.