My arbor press' ram goes all the way down flush with the base, so closing down the throat would never be an issue. But pressing a steamer wheel back on while the engine is still mounted in the body might require some extra clearance that the extensions would provide. Haven't done that yet, just surmising......
The parts you asked about were specifically designed and made for the Hobby Horse press. How you might adapt them to another press is up to you.
It is true that you will have clearance problems with some items if you try to use a standard wheel cup sitting directly on a flat plate. Some items are Turbines, Berkshires, and Gang cars. There are probably others.
By the way, I don't think I followed your comments on disassembling the motor trucks.
I reduce the size of the tabs in order to get them out of the slots by cutting back the edges that protrude past due to the staking. That leaves plenty of material to re-stake them on re-assembly.
Even though I own a press and lots of press tools, I use a 1/4 inch chisel and a hammer to restake the tabs.
I cannot imagine being able to split the tabs lengthwise with the chisel.
