math dullard here, but I learned a few months ago to divide the UNFINISHED unit size.
So if one of the units in the block is 2.5" Unfinished, and you want to do a 1/2 sized block
you'd start with .50 into 2.5 and get a 1.5" Unfinished unit. I think
you want to downsize by 1/3 so would you do .33 into 2.5? Or is it the other way around?
See, I'm just giving you time to find your wheel...what a friend am I!
Anyway, I'm thinking about doing some true minis, 1/12 the size of a 12" block.