I have deduced that this is in part because I am left handed, and that the way I hold my pen is incorrect, due to my primary school teachers were right handed and whilst they taught me well, I developed an incorrect pen-hold, which is apparently very difficult to correct.

So rather than go at length to improve my dexterity shortcoming, I suggest than an easier, less time consuming solution would be to make the pens with the screw threads going the other way. Of course, these would not be useful for right handed people who do not hold their pen correctly, but it would be helpful to those of us who have the odds stacked against us in gaining a correct pen hold.