this may or may not be of any use. I made the clipboard project the other day,

This was a super sized one. I wanted the edges rounded smooth with a bead look.

So I went around the whole thing 99% no filler, I was seeing pinholes develop behind the puddle as the arc was moved forward. I could let off the heat some and move back onto the pinholes and rewet it just a little then move forward easy and the pinholes would fill in.

Like maybe not enough heat to start with or moving to fast for no filler. Porosity is a pain to stop or get away from but if it bad technique, I believe it can be controlled by dealing with it as it happens.