In Tony Wright's article on setting up boat for single handed sailing (32kb PDF) he mentions having small blocks on the leach and luff to ease the necessary pull force when reefing.

Richard Gegenwarth originally devised an elegant arrangement shown in the photos below, with a cheek block attached through the existing grommet using a nut and bolt and a large washer on the backside of the grommet. His local North Sails shop stitched the loose hole on the block to the sail so the block couldn't rotate. 

After trying this setup for a while, Richard has advised that it did not work well as the reefing line would bind on the side of the block when the sail was "bent over" instead of smoothly running on the sheave. The design gave minimum windage and weight on the sail when flying the full sail, but did not like to be reefed!

He has now changed to a more conventional method using swivel blocks mounted through the grommets with stainless steel rings on the opposite side.