Oh ok,
I was going by
http://www.petitrc.com/setup/kyosho/...Bore/Chart.pdf
The rears are slightly heavier but the fronts seem a quite a bit heavier.
Comparing to the numbers on the Amain website of the spring sets.
http://www.amainhobbies.com/product_...ing-Set-4-pair
http://www.amainhobbies.com/product_...ing-Set-5-pair
But then Losi claim .05 lbs difference between their springs, and the chart you posted suggests much larger differences.
http://www.oople.com/forums/showthread.php?t=111137