Thanks Michael, as always, your explanations are very helpful to understanding my problem. I was right in assuming that the junction of those edges was my problem area. The second file that you attached (mq-8b_top3.3dm) was quite close to what I was hoping for. I was able to recreate the surface-to-surface fillet you created in your first example (had no idea I could do fillets like this). However, I'm not sure how you did the subsequent trim and sweep to fill in that triangular patch. Can you elaborate on those two steps a little?

Cheers,
Branden