DF: MM: Calculating the Weight of Giant Insects

Hi, Me and (anonymouse) are discussing this in Chat, right now.

VARIABLES
W = weight (in grams)
L = length (in mm)
LWR = length/weight ratio
GL = length (giant)
GW = weight (giant)

FUNCTION
L / W = LWR
LWR * GL = GW
(convert to imperial)

I know that's wrong, but that is just a starting point.
(Sorry, i never took algebra).

Can anyone provide the correct formula ?

Thanks,
Prespos