Why wouldn’t the Russian sub at sz115 just submerge and attack your placed transports in sz113? If you instead place in sz112, either the SZ127 Russian Sub or UK would blow them up. I don’t see how this strategy works… If you also build a DD, then maybe.
That is in fact what happened in my recent games. I do build a DD to place with the transport. I can also scramble 3 fighters if the sub attacks it. In fact, the better move turned out to be the sub submerged. On R1 the sub, 2 fighters, 1 tac attacked my BB and CV that were left. One game Germany won the battle but clearly defying the odds. The other time it was Russia winning with all the planes. I actually am considering waiting till G2 to attack the Russian CV and sub in future games.