I couldn’t agree more on the magnetic stylus holder. At the point they are just not strong or practical enough. It just sucks to lose the stylus on SP4 because it keeps falling off.
Here is a solution that I think will be practical and would likely please the haters of the loop from SP3: On the PF body machine a simple insert point for a clip. On the pen attach a metal clip like those on regular pens. When not in use one will take the pen and insert its clip into the opening on the side of the PF. The attachment will be as strong as the clip on the pen (or PF’s body).