There must be a misprint somewhere. They say the blocks are 45-50% lighter then stock blocks, but at the end of the article they say it is only 20 pounds (9.? kilos) less then a comparable alloy block.
2008 Galaxy Grey Miata Sport 5 speed: TDR2 Turbo Kit, Goodwin Racing Q exhaust, H&R front and rear sway bars, Tein Flex coilovers, Stock LSD added, and 17X9 Enkei RPF1's with 245/40/17 Dunlop Direzza Sport Z1 Star Specs
Back in the 80s, Ford built an experimental 2.0 ThermoPlastic block, twin cam engine. They bench ran it to an equivelent of 250k miles. I have no idea what ever became of it. I read about it in an R&D publication at the reaserch center , where I worked.