Spitfire Mk 26 - real or not real?

[Dark Star]

90% Scale is the linear dimension which means the effect on volume and therefore weight will be 0.9 x 0.9 x 0.9 = 0.729 i.e. 72.9%

Similarly 80% gives 0.8 x 0.8 x 0.8 = 0.512 i.e. 51.2%