18/24 is a decent flamberg build at a higher level, i tried it myself using a quite heavy armor (shynbaulds&rus scale), but i maxed out WM (thanks to high lvl^^), very useful if you want to hunt down archers while wearing plate armor. You dont need IF if you compensate it with your armor, but if you want to got for high level I would suggest you the build i have atm, which is much more powerful, but you need to reach 33 for it
Strength: 21
Agility: 24
Hit points: 56
Skills to attributes: 14
Ironflesh: 0
Power Strike: 7
Shield: 0
Athletics: 8
Riding: 0
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 5
On lvl 34 get yourself 8 WM