"Definitive Proof That It's SR?"

Why do you need to prove it? SR has it's time dilation effects--just read Einstein's original 1905 paper. That's where he calls it a "peculiar consequence," but not a paradox.

http://mentock.home.mindspring.com/twinrdux.htm
http://mentock.home.mindspring.com/twins.htm
http://mentock.home.mindspring.com/twin2.htm