so like, the strawhats arrived at alabasta right at nanohana town which is immediately to the right of the base beginning of sandora river, meaning that from the perspective of the wide shot of alabasta, the strawhats should have arrived from the bottom of the panel in the top left image. As some people are bringing up the idea that an island like drum island would be too small to show, i do disagree since as was also mentioned, the island climates aren't just based on the island, but they do extend a good bit outside the island, and if you look at the wide shot from below the sandora river, the fact there's not a single distinct weather change is a pretty big deal indicating that at the very least, drum island just cant be located there, i feel like if oda was able to clearly show sandora river as a clear landmark, then its fair to assume he's not showing any other islands like drum because there simply aren't any around.
Granted, i don't know how valid my take is since its probably partly occams razor, but i think it could be important to consider.
but if we could at least get some kind of hyper lowball, would it be a good idea to try to use the panel in middle right to get the absolute bare minimum for the distance between drum and alabasta, since size wise I'm not sure how big drum island is but i saw some calcs putting luffys bazooka range at around 20-25km, meaning that the pixel argument shouldn't work in that middle right panel as if drum would be there then it would be big enough to show.
Sorry if this post isn't super clear
Chapter 160
(this was the closest i could get to showingthe map of nanohana town, but its specifically page 5 or 6 in chapter 160 where vivi draws a visual map of the base of the river)