Permission "nolimits" allows to ignore inventory restriction. Also it doesn't work in Creative Mode.

config:
#number of slots

slots:
#Number of slots that are initially available, without any armor
startingspace: 1

#Number of slots that is given when wearing specific type of the armor.

leatherhelmet: 2
leatherchestplate: 6
leatherleggings: 6
leatherboots: 2

goldenhelmet: 2
goldenchestplate: 6
goldenleggings: 5
goldenboots: 2

chainmailhelmet: 1
chainmailchestplate: 5
chainmailleggings: 5
chainmailboots: 1

ironhelmet: 1
ironchestplate: 5
ironleggings: 4
ironboots: 1

diamondhelmet: 0
diamondchestplate: 2
diamondleggings: 1
diamondboots: 0

netheritedhelmet: 0
netheritechestplate: 2
netheriteleggings: 2
netheriteboots: 0