To avoid a tail strike, simply watch that you don’t exceed the rotation angle that causes your tail to touch the runway. It should be somewhere between the 5 and 10 degree mark. So maybe avoid exceeding 7 degrees or so.
Then with you limiting the rotation angle (and at MTOW, or whatever weight), there are only two things that affect when you lift off: speed and flap setting. So whether you are choosing 10 degrees of flaps or something else, you just have to accept the speed necessary to get lift off while holding 7 degrees of pitch up. Those are the constraints the flight model offer you.
I needed quite a bit of speed to start the positive rate of climb at MTOW with flaps 10 (let alone flaps 20)!