Anybody know what's this is about: you must have a current CMP Safety card to enter the ranges.
https://s3.uspsa.io/formc_details/6797/Staff Benefits.pdf
As someone that worked in an gun shop/indoor range the issue is fire. There is a lot of unburnt powder on the other side of the bench. Steel cases or bullets can spark, causing a fire. I seen it and extinguished them several times.
There shouldn't be any mag placement restrictions. Using a CO pistol under 'open' rules will allow the mags to be placed in front as opposed on the side by hip bone.