5 magazines is probably overkill unless you are using a 1911. Most stages you should be able to do with 1 in the gun and 1 on your belt.
Well, maybe... You need at least 5 to shoot USPSA, and there is a lot of crossover between that and multigun.
I believe that, given the present climate, the organizers are planning to reduce the round counts for the matches for the time being, so I guess you're probably right.
Amend that to three guns that RUN!!! Kind of hard to have fun when you're battling your equipment.
Ask me how I know!