Here's my setup:

I've done the Peter Pan thing, swinging on my trap wire WAY forward. If the bungie does NOT break you can recover and sail on. The only way to keep it from breaking is to make it have LOTS of stretch length...it must be long to start but still under tension.

If the grommet is a foot behind the sidestay (typical) then a straight line from the stay through the grommet aims at the rear beam and hull junction on the far side. I put a little block at that point and lead the bungie down through the grommet, diagonal to the rear beam, across along the rear beam to the block on the other end of the beam, then across and up through the grommet on the other side, forming an X. It's tensioned with lots of hidden length, 22 feet untensioned. That ought to be long enough!

On deck I lead the bungie to a block on a short tether off the sidestay and up to the trap hardware. This tether offers enough distance to keep the trap from winding around the stay.

The LONG bungie is always under constant tension. It does not get appreciably tighter as you move to the rear beam. When weather eats up the exposed ends of the bungie you have lots of stretch to cut off 18 inches and retie giving you fresh bungie.