I would go for a 20 amp ESC fused at 15 amps.
The real danger time is going from full ahead to dead astern, this can rack up the amps as the prop needs to fight against the foreward motion of the model.
If in doubt I am usually very gentle to get used to the handling characteristics. Then full ahead near the pondside where I am standing then chuck her full astern.
If she stops and runs astern all OK, if she dies she is at least close enough to recover.
If she blows fuse try a 20 amp and repeat.
If this blows you will have to get another ESC I am afraid, and run 1 ESC each motor.
Or get one of the cheapie Chinese ones, but they only give 50% power astern and if they blow only fit for bin.
My choice these days is ACTion as FLJ does a good recovery service.
Bob