Switch,
The Japanese fleet is no match offensively against the large number of transports (in addition to the full US and remaining UK capital ships) the Allies will have.
HOWEVER, upon further reflection, I think this might actually work if the Japanese simply parks this fleet off E. Canada (which effectively shuts off the shuck-shuck). While the combined Allied fleet is more powerful, both the UK and US fleet will still be weaker than the Japanese fleet and will suffer losses in trying to sink this fleet. Defensively, I think the Japanese fleet might be able to hold its own (transports cannot attack, except as cannon fodder). Additionally, there is the possibility of Germany landing fighters on the AC to replace lost Jap fighters, or even Japan sending fighters to Germany then reinforcing again after the UK attack.
I’m going to have to try this to see what happens - I’m still not sure if the Allies will have enough navy/airpower to clear this fleet without losing the shuck for more than a turn…