st93507

I managed B2B excursions in Scandinavia. Both were though Royal and there was about 2 hours between them which turned out to be enough time to grab lunch. 
My advice would be to plan for delays in the first excursion and count any time in between as a bonus.  

Also, you may have to mix an RCCL excursion with a non-RCCL one. I've noticed that ship excursions tend to all leave in the AM, and don't usually offer an afternoon option, unless its only an hour/ two hour excursion. But this could just be my experience on Caribbean-based sailings