Good luck!! I have been burned with kits as well -- my LQS made a fabric company replace bolts of fabric because they were off (she found out that they had shipped her a lesser quality because she was new and it was her first order and they did not think she would notice!)
I join the chorus -- with what you are doing there is no need to worry about cutting the stars straight. HOWEVER, since you are cutting triangles, I would still starch (or best press) to hold the shape.