Your build is fine.
These are my builds:
Level 30 (4 420 577 xp)
* Strength: 18
* Agility: 18
* Hit points: 53
* Skills to attributes: 2
* Ironflesh: 0
* Power Strike: 6
* Shield: 6
* Athletics: 6
* Riding: 5
* Horse Archery: 0
* Power Draw: 0
* Power Throw: 0
* Weapon Master: 6
* One Handed: 156
* Two Handed: 1
* Polearm: 1
* Archery: 1
* Crossbow: 1
* Throwing: 1
Level 30 (4 420 577 xp)
* Strength: 21
* Agility: 15
* Hit points: 60
* Skills to attributes: 2
* Ironflesh: 2
* Power Strike: 7
* Shield: 5
* Athletics: 5
* Riding: 5
* Horse Archery: 0
* Power Draw: 0
* Power Throw: 0
* Weapon Master: 5
* One Handed: 148
* Two Handed: 1
* Polearm: 1
* Archery: 1
* Crossbow: 1
* Throwing: 1
Level 30 (4 420 577 xp)
* Strength: 15
* Agility: 21
* Hit points: 50
* Skills to attributes: 2
* Ironflesh: 0
* Power Strike: 5
* Shield: 5
* Athletics: 7
* Riding: 6
* Horse Archery: 0
* Power Draw: 0
* Power Throw: 0
* Weapon Master: 6
* One Handed: 156
* Two Handed: 1
* Polearm: 1
* Archery: 1
* Crossbow: 1
* Throwing: 1
Basicly, i forgo IF and put those points into riding. Other than that, it's a standard 1h shielder build. You can fiddle around with maxing out either riding, athletics, shield or even weapon mastery. In my opinion, you should never neglect athletics as a 1h cav. Being fast on foot is important, because every cav gets dismounted and some maps are cav-unfriendly. Having the option to go on foot and do fine is most important.
I wonder if WM 7 is ever worth it.... and maybe even WM6. I use shield 6 in my 18/18 build now, because of the new slot system. Using the steel shield allows me to bring a medium wooden ladder, a siege shield or two construction materials when needed, instead of my huscarl shield (for on foot).