I ended up cutting pieces to add to the closure pieces so that they would be the correct length and it worked out very nicely. Here are the pictures:
The last 2 cushions may not make it through the summer - only was able to sew them with a 1 needle serger finish. While putting the new covers on the back cushions, the seam on the bottom that forms the box came unsewn. The seam didn't hold....oh, well. I'm done and next summer I'll just buy new ones because I will not be making them again! The fabric is a Waverly Outdoor fabric from http://www.housefabric.com/defaultproduct.asp and this is the pattern name http://www.housefabric.com/ProductDetail.asp?ProductID=28498.
I used Coats and Clark outdoor thread http://www.fabric.com/ProductDetail.aspx?ProductID=6f724c89-ff6c-49a0-af50-2ec09889a5c6 with a topstitch needle in the sewing machine and size 14 in the serger. The weave of this fabric is very loose and I think that is also why the 1 needle stitching doesn't hold up to stress.
Oh, and to get those new cushions into the new covers.....my Mother gave me the idea to put them into a garbage bag so it would slide right in, but someone on PR website went a little further with that idea. You put the cushion into a very large garbage bag then take your vacuum hose and suck the air out, then slide it into the cover, turn the vacuum off then cut the plastic bag off and pull it out of the cover. Worked like a charm!