Oh that is interesting So Chic regarding the Jean Muir hem finish - I just happen to have the book  High Fashion Sewing secrets by Claire Schaeffer and it is mentioned in this book - also found a reference to this on PatternReview.com.

Now just a few weeks ago I was asking questions about coverstitching, and of course the trouble I was having trying to get this looking right, and one of the snippets I picked up off the internet was to use strips of a wash away stabiliser and I used Avalon as I already had this,  I used two strips of this on top of my right side hem and the results are fantastic no tunnelling and the hem looks very neat.  By using this stabiliser it means that the stitch has gone through more fabric, and then when the stabiliser is washed away it gives more room for the stitches to settle in and thus no tunnelling.

Like you Sheilago I am new to sewing with today's modern knit fabrics, and on today's modern machines the only time I had stitched knit fabrics before was back in the 1960's/70's and then this was on a straight stitch machine and a ball pointed needle.  Now of course there is so much more to sewing knits and I am about to start on quite a journey - hope you have fun with this as well.  I also treated myself to a lovely book Sew Knits with Confidence by Nancy Zieman and I watched her video on this on You Tube as well - very helpful indeed. 

Thanks to others here on TSP I also bought some knit fabrics from Pound Fabrics, Birmingham, and they are beautiful, not at all thin and nasty curling knits but substantial jacquard type knits  ranging from £5.00 - £9.50 per mtr.  so I am going to be very busy.

I can't say I'm a fan of wrap dresses or tops either, they remind me so much of those old fashioned pinnys housewives used to wear many years ago, I don't know which era but possibly around WW2. Er no I'm not that old    but I've seen them on TV and in books etc.

I’m not a lover of twin needle work on  jersey.  Never seemed to get a good result. 
I prefer a 3 step zig zag to a normal zig zag.  It’s wide enough to make the hem lie flat and doesn’t give the problems that a plain one often does.  That’s a nice finish @Ouryve.  Not used that before. 
I used to use a feather stitch and also a Greek key stitch.  Either of those works because they go back and forth building in elasticity.  But they take time. 
Nowadays I have a cover stitch machine.  I sometimes like to sew it upside down.  It’s a nice look but is also so easy to get right to the edge of the hem!

Or a jersey needle. My janome prefers jersey needles, pfaff prefers stretch. Or it might be the other way round. Skipped stitches if I get it wrong so I soon find out.

@Lachica crudely drawn, the thread path I mean, is almost like two opposing runs of backstitch

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If I run that down the back just towards the point, it should take a little of the tension off the fabric at the front.

After fiddling around with it, I probably also need to pleat below the point slightly, which will bring the two seam allowances together. With a 5mm seam allowance either side of the cut, that leaves 10mm of material width bunched up under the infill piece, which is probably not helping matters. If I pull that bunch together into a pleat immediately below the apex, then do that curlicuetype stitch above, hopefully that will fix it up nicely.

As for covering it, more often than not, I tuck shirts and tees in. That said, the belt will cover the waistband, so there'll only be the point visible. As you say, probably not even noticeable... but if I can bull it up with a few extra stitches, it's worth an extra couple of minutes of faff.