Hello, and welcome to the slowest, but still the best ork forum on the WWW.
While I am a speed freak player, I have tried a similar list to yours (except no kans) and did ok. The foot slogging hoard seems to still be viable.
Of course, since you posted here I must recommend a few tweeks . Instead of having mega armor, put the big mek on a bike, this makes him one tougher, and faster so he can get to the kans to make a repair or keep them moving, and gives him a 4+/3+ jink save that works out way better than a mega armor save when shot at by meltas, etc. Better shooting too (twin link is an orks best friend).
As for the death coptas, go for the second FOC, (you already have the models and grots don't need hammer of wrath) this way you can split all your coptas into squadrons of one. No worries about failed LD tests sending the wingman off the board. They are either on the board or dead.
A sneaky trick is to make the grots your primary detachment, this way they get the objective secured rule, and it is a hoot to have a unit of grots trump a unit of vanguard for an objective at the end of the game.
The rest of my advice would be to something along the lines of adding in trucks and buggies, but I see your not really trying for the speed freak thing here, so I will let it go for now.
In the mean time, we are rebuilding the ork community on this board after a devastating dark eldar attack that had the board down for a few months and the majority of the former green tide we had here failed their LD tests and scattered to the four winds.
Glad to have you here, and hopefully we will have some more replies soon, otherwise I might have to
force erm I mean con,
erm, uh, talk you into becoming a card carrying member of the KoS.
My two teef