I used holes in the boom that were already there. The first one was for a boom vang, I think, and it is about 45 inches back from the gooseneck. The other one is about 40 inches back from the first one. These holes were all the way through the boom, and were each about 3/16 inch in diameter. I smoothed the edges with sandpaper a bit- I got tired of my main getting these little random snags. One of my goals was to make the entire boom as snag proof as possible.
Since I often sail with the poptop up, and since I don't worry much about sail shape, and since I am a lazy old fart, I don't have a boom vang. I also tried the 'roller reefing' on the main ONE TIME, and decided it was totally screwy. Rain on it.
The close up shows my 'attachment' methods. No fancy boom bail here- just some plain vanilla copper wire (stripped 12 ga romex) that I formed in a big loop and snaked into the holes, with the 'knot' inside the boom. Then I formed them into loops that I tie the 3/16 shock cord to. These copper things swivel a little, and when the lazy jax are down, the 'swivels' point to whichever side is tighter, and everything sits about flush with the boom. Call me lucky, call me a crackpot, it makes no difference. My wife thinks I'm a %#@!$&% Genius.
The drawing shows the basic layout. In brief, you go from attachment point to attachment point, keeping the shock cord snug, mebbe a little tight. Then you tie little loops in the midpoint of each section, and tie another piece of shockcord between these two loops, and in the middle of this section tie a little loop, which you'll use to tie the hoisting lines to. The hoisting lines (1/8" nylon) lead to cheap tiny hardware store blocks (tip: when in Rome, call them by their other name: "pulleys") that I hooked to the 'spreader dogs'. Decide for yourself if I made that last nautical term up. (Vote here.) I already had a cleat right below the gooseneck, which is what I loop the hoisting lines around when the thing is down and slack. Sorry I don't have a good picture of the whole rig up in action- maybe later.