It has been explained to me that the ratio of spine thickness to blade width should be between 3 and 4 with 3.5 (whoda guessed) a reasonable average. So a 7/8 razor should have a spine thickness of about .250" and 6/8 would want a .215" spine, where a bit thicker is OK. For honing, thinner spines than that seem to allow for more delicate edges which can be frustrating for us apprentice whetters to successfully deal with; the journey and master level honers among us may not be as potentially vexed.