After many decades of thought and study, I have come to the conclusion that the birth time can be off by as much as 15 minutes, in most cases, without dramatically altering the astrological indications IF we use some of the techniques applied by the ancients (such as the dodecatemory of the Moon, the Fortunata chart, Egyptian or Pauline dodekatemorion, various Lots) in our analysis.
Note: in the paper from the old Southern California Astro-Medical Club (1938 paper) which I mentioned earlier in this thread, the 1st, 5th, 7th and 8th houses (Placidus) were particularly emphasized in making a "potential trend" analysis; also Neptune was accorded nearly equal "potential indicative" status with Uranus. Parallel of declination of Uranus (or Neptune) with the ascendant, or cusps of the 5th, 7th and 8th houses, were also considered as equivalent to the placement of Uranus (or Neptune) in that house. However, in that paper, Parallels and conjunctions of Uranus or Neptune with Sun, Moon, Venus, oppositions or squares of Uranus or Neptune to the Moon, and any aspects between Uranus or Neptune with Sun or Venus, were given more importance in making the "potential trend" analysis, than house placement. Other factors were also considered, including the Hermetic Lot of Eros, and the Lot of Sexual Desire (taken from the oldtime literature)...