Hi Tom,
I have what you refer to as "mistake hubs" on my 1973 Paramount P-15, and have not had any problems with them (my current weight is 175). I worked at a Schwinn shop during the period these hubs appeared in the 70s, and don't recall ever seeing any failure(s) due to the extra drilling.
I seem to recall that all of these hubs were laced 4-cross, which probably helped reduce the stress failure from the extra holes???? I relaced the wheels with fresh DT spokes to replace the original galvanized ones.
Once was questioned as to the originality of these hubs on my Paramount, so I checked the dates on the locknuts, and they matched the date of the bike.
Photos of the bike and "swiss cheese" hubs can be seen at the following Wool Jersey links:
http://www.wooljersey.com/
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