This is fine for domestic loads, but anything coming out of a container (or going in one, depending on the destination) is probably going to be stuffed for transport efficiency (or best case, slip sheeted).
Palletised contained loads are rare in my experience due to the space efficiency loss (particularly at the moment with current freight rates). Even slip sheeting generally leads to shipping too much fresh air.
6% to 9% is on the low end - I would estimate the difference is closer to 20%. It’s at least 10cm per pallet, and assuming they are double stacked, with 10cm left on top for loading, that would be 30cm of the 2.5m height which is already 12% of the container fill before you even consider the space between pallets and all pallet heights not being at the absolute maximum allowable. It takes about 8 hours to unstuff a container by hand, so you can quite easily work out the trade off against shipment costs depending on your freight costs.
(My day job is a logistics consultant)
One advantage of Lindo is that it has a version that lets us integrate the solver into an excel spreadsheet, which helps us share the model with clients and makes it easier to explain to them (and let's them see the workings, as it's built in a tool that the client already knows how to use).
To hit 4.5 seconds cycle time on average, this thing is going to be cranking. I wonder what the centripetal acceleration required from the outside of the box is to let the arm complete its rotation in ~2 seconds is. That’s 180° of motion, with a start and stop ramp. Maybe I’d give them 3 seconds loaded if they can achieve 1.5 seconds unloaded. Will have to wait til after dinner to work it out, but it seems not a trivial force.