ive thought about flat ap but my thinking on that goes like this. i got my quints with straight ap which gives me 15 at start, plus the additional i think 2 ap at level 1 and with the base ap i think your sittin at 20~ at level 1. ap per level runes get better than straight ap runes at level 6 which is really when you need stopping power. so after trying it without the ap quins and with id say the early killing power is definately there now that i brought three ap quints as opposed to the xp quints i was using (the other option for the last utility point is 1 in the xp talent with 3x2% xp runes if anyones interested but not as good as this build imo)

so in short i have tried it sort of just backwards :P tried it without the ap quints and with and the extra level 1 stopping from the quints is def needed otherwise the extra help from def masteries doesnt do enough you cant live with mal early to dominate later. main thing with this build is pushing all the time so your going to be taking damage and without that extra ap from quint you arn't the last one standing early game

Just a suggestion. You don't have to try it. I think you should use Flat AP runes. These will help you get an early kill. Cause at level 1 you'll have more ability power. And since you have all your skills at level 3 you can probably pull off some combos for some kills. The extra damage will help you harrass even better early on.

Your mastery tree is very interesting. I might try it sometime.

You can take a look at my guide if you want.

I will try yours out and if it works for me, I'll +1 you.