Well, after a few votes in my poll, I've heeded the advice of Micromeister, who has a flying 1:48 Pogo. He says to go with a central 18mm motor so I went into the Dungeon and lopped off the back end...there was no going back then. I was a skosh hasty and trimmed too much off the root edge of the top stabilizer. I was going to fill the back end with SuperFil epoxy filler anyway, so I'll just have to work on this gap also.
I have the 18mm mount and 24mm stuffer installed. I also trimmed the tabs on the side fins and have the first one drying as I type. I used plastic cement on the plastic-plastic joints and epoxy where the tab touched the 24mm tube.
No photos until I fill my mistake.