P-51 and Dora are taildraggers, so I don't think that Yak experience would translate directrly to honing your skills with them. It's really fun aircraft to fly, but in my opinion the only thing that could be somewhat comparable is torque effect on takeoff. If you'd like to fly WW2 planes effectively I suggest more practice with them, and don't discourage yourself. It's like that - try to takeoff, crash, try to takeoff, crash... at some point it "clicks", and you suddenly know how to take off a Mustang. And might I suggest - practice the P-51 first, as it is easiest to fly of all the WW2 aircrafts in my opinion.