Originally Posted by Bartelby
Pardon my ignorance, but what is the significance of shared holes when it comes to strings? Any advantages or all disadvantage or neutral?
Well, in the days of wood racquets, holes were shared all the time, out of necessity given the lack of surface area to work with. But they also didn't have grommet strips that wear out over time. Folks also didn't re-string as often back then, when their non-existent poly would go dead after an hour or two.
From a MFR'ing and engineering perspective, I'd guess that the fewer holes you drill in a racquet, the fewer stress risers you introduce, so using shared holes could make the racquet ever so slightly stronger. The shared holes are probably a bit larger to accommodate two strings, but probably less an impact than additional holes. Not a huge amount, but probably measurable.
It might also be easier on the strings themselves with shared holes, at least in the stringing process. On my 18x20 93 Tour 10 Mids with none shared, there are adjacent holes in the corners where there's mere millimeters between one cross and its nearest main...so a sloppy stringer may inadvertently pull too hard or too fast and compromise, cut, or notch strings at the edge of the frame.
From a stringing perspective, it might be a bit harder to do, esp. with some stiff, kinky, or otherwise difficult string types, putting two in the same hole.
Since they've generally fallen out of favor, some (especially younger or less experienced) stringers might not have seen or worked on many, and potentially screw things up...esp. if they're unsure of the pattern, don't have their stringing manual handy, or it isn't otherwise obvious. The newer Heads I've seen with shared holes have visible indicators on the frame for the shared holes, besides a larger grommet hole.
Wear and tear wise, if you re-string a lot, I suppose over time the shared holes may wear out quicker, forcing the user to replace grommet strips more often. But that's also true without shared holes if you re-string often.
From an aesthetic standpoint, some folks may bristle at them. Snobs may think it's a granny or Wal-Mart stick, not that there aren't a ton of granny sticks out there now already without shared holes.
I'm sure someone from USRSA or the Stringers Forum can add more insight and practical experience.