Hmmm - you might be right AnitaSt - that the length of the join probably isn't helping matters. Also, I am wishing I had done a straight cut. I did wavy as that was what I saw recommended (and it made sense - the reason why - having to do with the integrity of the quilt). But as I was putting it back together, I was wishing it was a straight seam.
Well, first things first - and that is I am going to FMQ the one side that I already have put back together. By then I should be rejuvenated enough to tackle putting the last side back together.
I think I will do a couple of things differently for the second side. I am pondering starching the back before I add the batting. Then I will tape the backing to the floor (don't know why I didn't do that for the first side - might have solved some of my problem). And cross my fingers that it will go better the second time around.