I think that you will be pleased will how things fit once your blocks are trimmed. With 6" squares used in the blocks, even if you have to trim off a little bit here and there, it won't be so noticeable within the block. If the original squares used to make the block had been small, then trimming might have left the edge rows looking too narrow.
I have used Elmer's school glue on bindings before, and maybe it would work to use it to baste the sashings down if you do the whipstitch method for attaching the blocks.
Dayle