>we'd put an AP at the end of each aisle staggering the AP location (top or bottom) every other aisle.
By Google's calculation, that is an Isle 122m long. I think the results will be crappy.
I think I would go with ceiling mount, with the APs being 20m, 60m and 100m along from the end of each Isle (so 3 APs per Isle). At 4 APs the coverage would be quite rich.
Do your scanners have the option of taking an external antenna? If so, you could put an actual antenna on the top of the forklift pointing back up to the roof. Or even a simple high gain Omni.
Another interesting twist would be if you could get Ethernet-based scanners, and then put an AP on each forklift (so the forklift units would act as a wired MESH repeater node). Never tried that myself.