I grew up as a JW. The first time I heard anything of Russell's 1914 pyramidology theories was through a brother in the early 1990s. I was about 17. He wasn't a conventional JW by any means, and he wasn't brought up in the truth (I think he's no longer a JW).
We were out witlessing when the topic of CTR and 1914 came up during conversation. He said something like "He went a bit wacky with pyramidology". That phrase stuck with me for 15 years until the internet came of age.
Whenever talking to JW's about "Old light" I like to use Luke 8:17 - "For there is nothing hidden that will not be disclosed, and nothing concealed that will not be known or brought out into the open."