Actually, there is a very simple trick to make them come out flawless.
After making the initial cut on a cap block, place it on the wall where you intend it to go, next to the previous block. (I'll assume there was a little undercutting or overcutting because of the type of saw.)
Slide both cap block back toward the retained soil just a bit, so that the front face is behind the face of the SRW units below it (but those two cap block are still touching eachother). This is done to protect the front edge and face of the block below the caps.
Now drop the saw into the seam between those two caps and saw completely through them, top to bottom, front to back. Make sure they are supported on each side, so that they can't move while being cut.
In doing this you are allowing the blade of the saw to grind away any small imperfections in the seam, and repairing any overcut or undercut.
If a gap in the seam isn't repaired with a first pass (the flaw is larger than the width of the saw blade), snug the two caps together again and re-cut.
Piece-o-cake.
