This small fiddle block mounted on the aft end of the boom will change the mechanical advantage from 2:1 to 3:1, a 50% increase in your ability to sheet in the main.
Use your existing Carbo traveler block (pictured below under "May we also suggest") as the bottom block of the tackle. Tie the standing part of the mainsheet through the hole in the center of the large sheave of the traveler block, essentially making it the becket. Next, lead the mainsheet through the small sheave of the fiddle block mounted to the boom, lead back down and through the large sheave of the traveler block, back up through the larger sheave on the fiddle, then finally, forward through the already existing block in the center of the boom.

• Shackle pin diameter: 5/32"
• Sheave diameters: 1-9/16"" & 7/8"
• Maximum line size: 3/8"
• Safe working load: 485 pounds
• Break load: 1620 pounds