Well, now this is just my humble opinion, but here goes... why do you feel it needs more quilting...I think it looks like it has plenty just the way it is and it looks great!!!
Otherwise, I think if you feel the need to do it....if you hold things flat enuf as it goes into the machine it shouldn't pucker too much...your apt to have some.... are you doing this with your regular machine or do you have a longarm?