Well... I was wrong. I put together my muslin last night and the fit is way off!
First, I took a quick trip to Dressew and bought a french curve. Best $2.99 I've spent all week! Upon using it, I realized my tape-dispenser method wasn't as bad as I thought, but the curve is still a much cleaner way to go about things.
After taking care of that last change to the pattern piece, I cut out and sewed up my muslin. (Quite poorly, mind you. Please ignore the puckery princess seams and the fact that part of the shoulder seam allowance is on the outside. I'm not going for "wearable muslin" here, so I'm not concerned.)
First, let's take a look at what I like. I pinned down the neck and shoulder seam allowances on one side so I could get a better idea of how the finished piece would sit. I love the look of the princess seams down the shoulders, and I'm definitely happy that I opened up the neckline. The width of each strap (is that the right word? Or shoulder?) is perfect, and the full bust adjustment seems to have resulted in good proportions.
Next, what I don't like. Mainly: the fact that it's way too big!
I know this top needs to have some ease due to the lack of closures. Also, I know it'll hang differently once I make it up in charmeuse. But seriously - while the proportions are right, even the bust is ridiculously large.
To think - when doing the tissue fit, I'd actually been worried it would come out too small! I suppose I can see how experienced sewists bypass the muslin and go directly from tissue to final garment, but I'm so glad I went about things the practical way this time. I couldn't have been more wrong.
To get an idea of how it should fit, I laid out my favourite ready-to-wear silk blouse on top, which is a similar silhouette and also lacks closures. It was almost comical.
There's about two inches of extra fabric on the muslin on each side - about four inches total. Yikes!
So, the next step is to figure out how I want to deal with this. I know that part of the problem is those two added inches from the FBA. But there's at least another two inches to be shaved off as well. I'm not sure if the best move would be to simply remove the inches from centre of the back and front centre peices, or if I should start from scratch and cut a smaller size?
In truth, I think width of the back from armhole to armhole is too wide (I couldn't get a photograph myself, but when standing straight there's vertical creasing by the armholes in the back), and I think the princess seams could stand to move inward a smidge, so I'm going to try the easy route and simply remove the excess from the font and back pieces on the muslin. If that doesn't look right, then I'll consider starting from a smaller size.
On the bright side - I forgot how fast sewing is! After years devoted to knitting, that's refreshing. (Because there's no worse feeling than realizing that you need to rip out an entire hand-knit sweater!)