Shielding is cheap. I added a disc to all of my thicker neodymiums. Got the shielding off Amazon.
Pins are pretty much useless for internal bows & warps 
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Are you sure you don’t mean neodidliums? (thank you, Marion) 
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The problem with pins, as articulated by JamesDHatch, is that they can only grab the edges of the material. If I’m going to cut a circle out of a piece of paper, I need a hold down in the center of the cutout to keep the air assist fan from pulling it out and blowing it across some other area yet to be lazed. Or if the material is bowed in the center, magnets are the only option for holding down the inner regions of a piece of stock.
Flux rings (or in this case, “plate”) is a good idea. An Iron “cap” covering the top and sides of the magnet will significantly reduce the magnetic field emitted upwards while simultaneously increasing the field strength emitted downwards…
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When mining and dividing out the various chemicals in the lanthanide series there is a pair that is very hard to get apart. The neodymium and praseodymium are therefore used together as didyminm particularly as a colorant in glass best known as glassblower glasses but if you put your hand in the meat display and it looks like a nice steak then the lights are colored with this material.
I could be wrong but I suspect that the neodymium in magnets does not include the praseodymium.
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I use magnets from retired hard disk drives. The plate they are attached to and the way the magnets are poled results in almost no field on the steel plate side and NdFeB strength on the other.
I make hard disk drives for a living (or used, to, anyway. It’s all about SSDs now. And they have no magnets. 
)
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