Hi,
I have made many lone stars and when I sew the star sections together, I sew it slightly wider going in towards the center. I have never added the squares and triangle at the same time.
If you put it together 2 by 2 and have two half done stars then sew it straight across to join the two halves (as someone else mentioned) I start scant...then widen as I get to the center then slowly work out to scant.
It is true also it can be quilted flat if it isn't too bad. I ask my quilters to do a scribbley design in the center middle blaze and outside diamond (makes it look like it was done on purpose) so the not all the lines end up meeting in the center and puff it up.
Also and all over design flattens the bump if it isn't major.
Yours is kind of major. If it were mine, I would separate (rip)the 8 points in the center about halfway out and resew them with a bigger seam. Sometimes you can applique something in the center and cut out what is underneath (like the bump!)....I have put things in the center of my lonestars.