Last night I just kind of tried it out with the too-wet feed, and it was indeed too wet. it was a bloody firehose and made the F nib write like a B/BB with any more than the lightest touch. it's a semi-flex nib, but this feed was just overkill.
I kind of took everyone's advice - sans the sanding, plus the info I was able to find online, knocked it out again and went at it in one more shot with the drier feed.
The section was cleaned in my ultrasonic cleaner prior to all this so there wasn't any gunk. There really wasn't any mark in the section where the nib was before, even careful inspection with a loupe showed no real indentation.
I set it up in my knockout block (2 inch thick piece of wood with a 5/16th hole drilled in it is the perfect diameter/depth, lets you knock the nib/feed all the way out without touching the table below). took the nib/feed in my left hand and coated it with dish soap. I took my heat gun (way too powerful for this work, I wish I had a hairdryer but my wife has curly hair, so no hairdryer in the house) and set it to its lowest setting (again, way too hot to use up close) and held it a good two feet away, blowing all over for about 30 seconds. I then set the nib/feed in, grabbed some pliers with a piece of thick motorcycle tube between the jaws, and gently but firmly squeezed and pressed, and it slid in firmly, but tightly, just as I'd have hoped it would go in the first time. Tight, but in the right kind of way.
Cap fitment is perfect, nib feels right. Ran it through my ultrasonic cleaner for 5 minutes to get the soap out, filled it up with Sailor Tokiwa-Matsu to match the green celluloid, and boom. it's perfect.
I like that fuel line and pliers job. I have fuel hose and some old beat up slip jaws sitting in the garage. I'll make one today for that!
Thanks for the advice everyone, it all helped.
Last question - I know the sections are supposed to be held in with some sort of shellac. I currently just have silicon grease in there to seal it up. Do I need shellac? if so, which kind?
Edited by Honeybadgers, 28 June 2017 - 18:59.