The way my ETL has our custom blocks set, if we have a three tier U-boat, the aisle numbers are divided up. Like for toys, aisles 1-5, top shelf aisles 6-9 middle shelf; and that's how most of our u-boats are done. The worst is pets. But I guess at my store the emphasis is going towards accuracy as well as the time of how long the unload takes. Used to its been about speed rather than accuracy. I can't stand my Uboats being overstocked and boxes falling off, its an injury waiting to happen. And yes our backroom/recieving has been tweaked around to make room. As well ppl do make mistakes on the sorting, but if all is to be where your lead is to audit that sort, they'll point it out.