Tie a spectra line to each double block. Install a camcleat on each side of the mast. Run the lines through the grommet and cleat them. This gives you an additional 2 to 1 multiplier on your downhaul. It's a cheap light way to increase purchase.

Hints:

Use 1/3 line and the big Ronstan cleats, the small ones break

Before you drill any holes, make absolutly sure the cleats are in the right place.

When your are rigging the boat, let you downhaul out all the way and pull the lines tight when you cleat them (basically pretension the sail to the minimum downhaul). This gives you the maximum travel for your downhaul