(The actual colour of the ink after drying a while is much more day-glo orange than the scan looks on my screen.)
Pilot Petit1 and Petit3
It turns out the fountain pen is much more comfortable to hold without the cap posted (stuck on the back). It still needs to be held at an odd angle to get good ink flow with this ink.

I’m told these pens can also be converted to “eyedroppers” as long as there are no tiny cracks in the body of the pen. Basically, you unscrew the body of the pen, remove the cartridge, add silicone grease to the threads (and a tiny O-ring if the construction of the pen allows it), and then fill the entire body of the pen with ink (with, say, an eyedropper). That way, it will hold more ink. That way, if it isn’t a well-constructed and/or well-greased pen, you will leak ink all over everywhere. Fun and profit!

So petite!