When Alex Gregory originally came up with the design for a 7-string guitar he intended that it have a high A string, rather than a low B... The True History of the 7 String Electric Guitar.
Eventually, he realised that the world wanted a guitar with extra low frequencies, and after a couple more 7-string prototypes he abandoned the 7-string idea altogether and instead proposed a 5-string tuned in fifths, and thus having a greater range than a 7-string tuned in fourths. And thus was the celloblaster conceieved. See: www.pentasystem.com