To make the upper portion of the bulkheads nest properly against the cabin cover, I marked the contact area between them, and sanded that flat:
|Bulkhead attachment surface after only partial trimming|
|Flattened bulkhead attachment surface|
For the door inside flanges, I read several reports of people that trimmed too much off and had to rebuild it (VAF post) and recommendations to not fully trim it until I'm fitting the doors (VAF post 1, post 2), so I trimmed it but gave ample margin from the suggested 1" from the bottom, and from the side scribe lines:
|Markings for cutting the inside door flanges, well below the target 1" distance from the bevel|
|Plenty of margin between the scribe line and my cut|
|Inside door flange, trimmed far from the scribe line|
I looked at several photos from other builders (like these and these) and they all seem to have trimmed more than this, so I should be fine with final-trimming later with the doors. I do plan to use the McMaster-Carr seal (post).
I realize this means there'll probably be a second cut later to adjust these, but at least I can drill and countersink the holes along the flange without interference.
Towards the end of this process, I found the the Dremel rotary tool actually cuts the fiberglass much more easily than the oscillating tool, and while it makes a bigger mess, it's basically a "directed jet" of fiberglass dust, so as long as I stay away from it, I actually get less fiberglass on myself:
|"Working with fiberglass is not messy at all", said no one over|
Besides that, I had several more passes of trimming the various flanges to fit well.
|Cabin cover fitting well on the fuselage|
Now that it fits properly, I can start drilling the attachment holes.
P.S.: OMG I hate fiberglass. How do people find it fun to build entire airplanes out of this?
Total cabin cover rivets: 0
Total cabin cover time: 27.6h