The standard training mission has you taking off from Vazani, where the runway is a bit narrow. For me, it helped to make my own runway takeoff mission from Batumi, so if I went too far to one side, I would be able to correct it before rolling into the dirt and spinning out/cartwheeling.
As for the aircraft's tendency to flop over to the left upon leaving the ground, I learned quickly that I needed to watch the needle, like Roadrunner said.
I agree with Roadrunner that it's a good idea to have the rudder set to the right; additionally, I have my ailerons already off to the right before I even begin to roll. I refer to it as setting my "trim". I raise my flaps up all the way, because I'm not in that much of a hurry to get off the ground- there will always be plenty of runway.
Personally, I prefer to just push the throttle up to 100% and let the Kommandogerat do its job. If I have my "trim" set too far to the right and my plane begins to bank to that side, I can simply move it a little closer to center until it evens out, instead of having to frantically fight the plane to keep from flipping over. I'm not perfect yet, but my success rate is around 90% and my survival rate is around 98%.