5ps is doable, but difficult. Prepare to glance. 18 STR 6 PS is the minimum for non frustrating melee, but as an 18/21 build is simple it's pretty easy to make an agi shielder with decent striking power.
Suggested 18/21
Strength: 18
Agility: 21
Hit points: 63
Skills to attributes: 8
Ironflesh: 5
Power Strike: 6
Shield: 5
Athletics: 7
Riding: 0
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 0
One Handed: 111
Two Handed: 1
Polearm: 1
Archery: 1
Crossbow: 1
Throwing: 1
Alt 18/21 (Heavier armor):
Strength: 18
Agility: 21
Hit points: 57
Skills to attributes: 8
Ironflesh: 2
Power Strike: 6
Shield: 5
Athletics: 7
Riding: 0
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 3
One Handed: 130
Two Handed: 1
Polearm: 1
Archery: 1
Crossbow: 1
Throwing: 1