Simple maths - the bigger the dia. then the bigger weight savings for a given wall thickness (which is why it's worthwhile on the front triangle). Chainstay weight saving is nominal, seatstay is miniscule. If you really want to geek out I can send you a spreadsheet that'll show the weight savings you get for all that hard earned £
It's more a calculator based on all carbon steel weighing approx the same - enter your tubing overall length, butt lengths, wall thicknesses and it spits out a number at the end.
Simple maths - the bigger the dia. then the bigger weight savings for a given wall thickness (which is why it's worthwhile on the front triangle). Chainstay weight saving is nominal, seatstay is miniscule. If you really want to geek out I can send you a spreadsheet that'll show the weight savings you get for all that hard earned £