Planetoid SIze??

I'd like to know if anyone's worked out a system to convert the size of
planets from the SJ way to a number in  miles? I'm designing a new sphere
using the World Builder's Guidebook and would like to use the world size
tables but I don't know what the equivalent is in SJ, i.e., Class A, B, C,
D, E. What do the letter classes convert to in miles and such?

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A star rushes past, to crash upon the shore
But the first of many many more
Stoke the fire and stout bar the door
For this is the night mages go to war


Toby Mekelburg
toby@????.net
mekelbur@??????.edu
Tobymeke@???.com-"Hey, those sign up disks are everywhere!"
http://www.lava.net/~toby