I recently replaced the packing on my 26. I think the book is incorrect, there is no way 1/8" could seal a 0.75" dia shaft. The original packing around my 0.75" shaft looked like 1/4". After 12 years it's a bit difficult to tell! However, 1/4" nor 3/16" worked well, and I finally after 2 hot Saturdays, fitted 5/16" and it sealed.
This required a little more "grunt" than I would have liked.
I wonder if in 1988 Ericson were fitting any old parts they had lying around and never changed the documentation, hence the issue. But, after 12 absolutely dry years I can't complain. In fact the mechanic at the local yard chastised me, by saying if I had been more careful and adjusted more regularly it would have lasted 12 more.
Hope this might be of some use
Rob