Tim,
Another way to mount them is by taking a single soft loop between your thumb and forefinger and pull it tight by pulling upward on the bobbin after you go around the hook shank.
In other words:
1) you don't pull the soft loop tight in the normal manner;
2) instead you pull it tight after the bobbin is taken around the bottom of the hook;
3) which means you pull it tight by pointing the bobbin at the floor and pull up when the bobbin is on your body side of the fly.
4) Make 3 wraps this way (one after the other) with a very small space between each wrap (like a width of a thread wrap or so) remembering to keep holding the wing tight and pulling each thread wrap tight by pulling up on the bobbin as described.
5) Then check your wing's set and if it has moved to one side or the other, gentely move (persuade) it into the verticle proper position by using the thumbnail and forefingernail of your right hand while holding onto the wing firmly with the thumb and forefinger of your left hand. Remember, a little goes a long way when doing this, so check your wing's position after each very (and I mean very) little tweak of its position.
I learned this method from Judy Lempko (she lived in Texas and was a superb tyer of classic married wings) many years ago (must have aroung 1981) when she was doing a tying demo at a FFF Conclave in West Yellowstone, MT. It will feel odd and awkward at first and will seem completely counterintuitive, but stick with it and after 10 or so flies it will start feeling OK to tie them this way.