So Taerkitty sent me some samples to test out. In 14" CPVC, with a PumpBow, I couldn't hit a doorway 30' away due to dart spiraling out of control. With thickwall PETG, and a 4B, I had the same issue, out of control spiraling. Were they well made? Sure, cool idea, but keeping the glue tip centered in the foam is nigh impossible. I even removed the nuthead after the dart ripped (after 3 shots hitting skin, I might add) and put in on my foam, using medium wall petg and a PumpBow again. Another spiral, this time cracking the head.
They are simply not heavy/aerodynamic enough to work well with powerful guns. The nuthead was just barely thicker than the foam, making easy loading into barrels difficult. The pain test was obvious, I was able to tell the difference between these and slugs everytime, blindfolded.
Slugs are extremely simple to make, and very inexpensive. Plus they work in hoppers. These do not.
I don't hate the idea of new innovative dart-making, but this isn't the best way.