Where are you attaching your pen tab to your Surface Pro 3?

The pen comes with a little loop to hold it but no instructions anywhere about where to stick it.

I cant figure it out myself

Like this!

Cool stitching work, Mick!

I went with the Leuchtturm1917 loop (they sell it on the Microsoft Store and Amazon, but I bought mine in a bookstore).  Much tighter than the existing loop.  I now have the original (red) loop on my keyboard, same place you stitched yours, and the 1917 loop attached to the top right of the tablet.  I trimmed the adhesive pad of the 1917 so that it sits flatter -- the embossed Leuchtturm brand made the corners lift up.

It's nice having these 2 options for putting my pen. :) Before I got the new loop, without the keyboard, I used to stick the pen's clip onto the magnet of the power source, or where the keyboard attached, but I was always afraid it would fall off.  

I think if the pen clip were redesigned a little bit so it fit in either the charger slot or the keyboard slot, that would be much more useful.  I never really actually clip the pen to anything anyway.

Cool stitching work, Mick!

I went with the Leuchtturm1917 loop (they sell it on the Microsoft Store and Amazon, but I bought mine in a bookstore).  Much tighter than the existing loop.  I now have the original (red) loop on my keyboard, same place you stitched yours, and the 1917 loop attached to the top right of the tablet.  I trimmed the adhesive pad of the 1917 so that it sits flatter -- the embossed Leuchtturm brand made the corners lift up.

It's nice having these 2 options for putting my pen. :) Before I got the new loop, without the keyboard, I used to stick the pen's clip onto the magnet of the power source, or where the keyboard attached, but I was always afraid it would fall off.  

I think if the pen clip were redesigned a little bit so it fit in either the charger slot or the keyboard slot, that would be much more useful.  I never really actually clip the pen to anything anyway.

I attached mine right out of the box in dustless environment, using high pressure clips told hold in position and a heat gun to activate the glue.. left to cure for a good 24hrs before sliding a pen into it.  And it stuck well for about 3 months. It was the quick pulling/pushing it in-and-out of the bag action that eventually shunted the loop's plastic section with adhesive underneath open and it folded back into a crease. From then on it was screwed. Like that game "Pull the handbrake at anytime, it's a surprise!" This thing was falling out twice a week at surprising timings and locations.

Yep! So the answer to this discussion's headline "Where are you attaching your pen tab to your Surface Pro 3?"  is... Custom Fittings Required.