Hi, Yep, that is my pdf.
I have never got my mitts on a 19. The later plastic ones were not sold in the UK, so hardly ever come up on ebay.
I have PMed the admin of the funface group. Somebody a while ago had a similar issue when trying to join.
Last members to join are showing as two weeks ago. There is only one admin and no mods for the group, so only one person who can approve requests.
Post some photos of the 19, with the top off, might be able to give some ideas.
In general, the Zenits without top mounted light meter had very little light sealing in there. There was no need for it, as light could not get in the top anyway.
Use a strong torch (as described in one of my guides) to find any possible entry points for light & add baffles or foam. Light will always work its way backwards, through the viewfinder, into the prism and then into the mirror-box. This light should not find it's way onto the film, but on some Zenits, it could get through and around the mirror, when it is up, so I add thin dense foam to the underside of the mirror and along the front edge. These are shown in my guides, if you can ever get into the funface group
)