It's hard to say without watching you to see what exactly you do wrong. At the end of the day do you stack because your shelves are full, or is it because there is just physically too much volume to pull and load at once?
Some tips for efficiency.
I don’t organize commit time airs(the ones with 1000-1100 hin#)stop for stop because the driver will usually look through those as soon as he gets in the truck, waste of my time if he does it. At the same time make sure they are all there together so your driver can find them.
Learn when a box/stop is too big for the shelf and when to drop it to the floor, like most trucks have resi on shelf 7-8, you can bury a 7-8 resi under rear door stops because rear door stops come off long before the end of the route.
The RDL stop on my 2d truck gets a lot of smalls, but also a lot of large heavy packages so loading them as they come doesn’t work when the small ones come first. I put the smalls on the back of shelf 8 behind the metal clipboard thingie so I don’t have to worry about moving them so they aren’t crushed by a large package, I have also seen loaders use a smalls tub for that too.
I stack at the end of the day, but I do it the right way. I stack things that I will load last, like bulk stops that there is no room for, I could load them but that would take time to rearrange the load and I would end up with more stuff stacked out.
Try to remember what areas of the truck are full, if shelf 3-4 and the floor below are full don’t try to load a package for that shelf when your getting slammed at the end of the day, it will take too much time to rearrange the shelf so there is room, and you will end up with more stuff being stacked out.
Make smart decisions about irregs, some can be loaded but many should be thrown in last because they take up too much space and take time to work around.
Make use of all the space in the truck, if there is room on shelf 5 and your RDR stop is overflowing throw some light packages up there, but let the driver know. What I do is pull the SPA label off and write where I moved the stop, then stick it to the steering wheel. Works well with over 70’s and irregs too.
Check the address label, I look at the zip/street quickly before looking at the HIN #, sometimes shelf 1 stuff ends up on shelf 6 for whatever reason, and of course bad labels/computer errors.
Prepare for work, make sure you get enough sleep, I aim for a solid 6 hours every night, then bout 10-12 catching up on the weekend. I wake up, throw a couple potatoes in the microwave then take a hot shower. After the shower I stretch out, then eat my potatoes, baked/mashed or fried so it doesn’t get too old eating the same thing. Usually have an energy drink with breakfast, it makes a difference and they are like $1 each at Costco. If I am late getting up and break the routine my performance suffers.