I don't think the 688/688i carry enough processing power to perform the necessary calculations... considering the SW was built without utiziling COTS from scratch (the TB-29 currently on the 21/22 are of the legacy variety as far as I can tell), I'd say it's the same for the 21/22 (JC probably has more significant COTS implementation so may already be utilizing the TB-29A, the COTS variety of TB-29).
So, the issue of twin-TA utlization is more an issue of computing power than physics for US subs currently... so the ambiguity stays for US subs. Nice try though.
