Mike's idea makes sense and explains what the blocks inside the the beam are for. I checked the bungie that broke and it was not long enough to be set up that way. I saw in the Viper rigging instructions that a "control line" was rigged up as you describe, but since what I was replacing wasn't rigged that way, I wasn't sure that it was necessary... The Viper instructions call just about every line a "control line" and I wasn't sure what the diagram in section 5.2 represented. I will look at the Vipers this weekend and see what's going on inside their front beams.

That's got me curious though, what about the shock cord for the skipper? On my boat the cord goes from the starboard trapeze, under the tramp directly to the port trapeze. There isn't any room for peter panning on it either...