CORRECTION TO ORIGINAL POST: I am sorry I have confused so many, guess I'm having trouble explaining.
FINAL CORRECTION - THE EXTRA PIECE WOULD BE ADDED ONLY TO THE BOTTOM OF MY 50 X 50 SQUARE. (the square was not 50 1/2.)
I agree the figures would be easier to work with if I added 10 inches at the bottom, then I would have exactly 50 X 60. Bearisgray - your illustration "B" would be what I need.
Now, what size blocks would I need to make to go all the way around my 50 X 60 inch rectangle? 10 inch? 10 1/2? or less?
I want to thank everyone for your help and I am sorry I have confused some - I get confused myself, ha..ha..