Here is a historic detail on a 30 year old home built ketch just back from a cruise to the US. She is still owned and sailed by her designers/builders, a vigorous couple. There are advantages and disadvantages to side by side twin stays.

• They make flying twin jibs off the wind easy.
• You can have two different headsails set and ready to use.
• There is a backup headstay ready to support the mast.
• Backstay tension is split between two stays, so both will sag more reaching and beating  leading to a fuller sail shape, which you do not want.
• There is extra windage and weight aloft.
• When the s tays are close like these, on occasion hanks will attach themselves to the opposite stay, creating a real hassle.

When we built our 62 foot cutter, Intermezzo ll, we used side by side twins. They were set a foot / 300mm apart. The system did work well, and we  put many thousands of miles on it. But we never used them again, primarily because of the difficulty in controlling sail shape due to the aforementioned headstay sag.

Today, with free flying code zeros on furlers, the twin headsail off the wind requirement can be better solved with a working jib on the spinnaker pole to weather and the code zero to leeward