Thanks. It's curiosity, not worry. I've seen larger total area openings on steel frames, but this was unusual for Litespeed frames and wondered whether there might be a reason for it.
I recall Litespeed marketed this frame at the time as the lightest production frame on the planet. Maybe it was the larger diameter hole that made the difference between lightest and second lightest. ;-)
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WTB: Slingshot bicycle promotional documents (catalog, pamphlets, etc).
WTB: American Cycling May - Aug, Oct, Dec 1966.
WTB: Bicycle Guide issues 1984 (any); Jun 1987; Jul, Nov/Dec 1992; Apr 1994; 1996 -1998 (any)
WTB: Bike World issue Jun 1974.