I've been thinking of DPS Tanking Cho as well. With feast you get a respectable HP regardless of build and you get true dmg from spikes as your primary atk. I was thinking of adding atk spd to try and really take advantage of this. The build I'm looking at though is: Rod of Ages -> Boots of Swiftness -> Malady -> Will of the Ancients -> Nashor's Tooth ->Rabadan's Deathcap

I'm also tempted to try this with Archangel's instead of rod for max AP, but I like having a little extra HP to start.

Also for Runes, I would recommend static AP for glyphs and quints. the total AP bonus is fairly insignificant late game even with the progressives, but starting with 35-50 AP is huge if you take improved ignite and start with a ring. that gets you starting approx 50AP, which is great for early kills. Seals I do all mag. resist, combination of static and progressive, and marks Atk Spd.

Remember with DPS Cho deals almost all his damage with spikes, so spell vamp is good (they're magic dmg). This also means you get to be big tanky DPS who's immune to thornmail, and that seems really good.

I'll try to figure out what will happen if Manamune will be replaced with Atma's Impaler right after Warmog's Armor.

Great Build, I'm getting Cho with IP tonight, I will try it out :)