That's correct. They used "vinyl glazing channels", same as camper trailers of the era.
Robert at VintageTrailerGaskets.com has been very helpful
Steve at VintageTrailerSupply.com turned me on to DK Hardware (search: vinyl glazing channel)
Still trying to pin down the exact one, but Robert has a interesting library on his website, some of which show how you would just make your own.
....instead of having goop smeared all over the cabin top that you essentially spent twice as much on.