String size is one thing, the other is the length of the bass in general - some work better with low tunings/some don't
But usually you should be able to do drop d easily with "normal" ones, everything below I would increase the size atleast 1 per half or full step
I wish I would have more time to do currently more than 1 try for every song, so atleast on bass this could have been the first 100% week then, but well too much todo...