When we de-rigged the mainsail last season, we noticed that three of the plastic D shackles that connected the sail to the mast inserts were broken (see picture). We cannot locate plastic replacements at our local marine stores. So, we have a couple of questions:1. Can we use metal D shackles with the clear plastic guards?2. If not, does anyone know of a source for the plastic shackles? The sail was made by Neil Pryde, and they don't seem to be in the sailboat market any longer.