Holder was a private project on an other forum, not publicly sold.
About the spacing; I think it is quite spot on for the lower set of holes. Flames cover all of the bottom of pot without going outside the flux ring. So minimal loss of heat.
I've done hundreds of boil tests over the last few months to optimise a Jetboil pan on an Evernew or Evernew type burner like yours. The optimal positioning of the burner between the top burner jets and the pot base is down to a change of a matter of millimetres.
The optimal setup does have a fair amount of heat going through the Heat Exchanger, without this the Heat Exchanger doesn't work, so your observation about minimal amount of loss would work for not melting your pan sides, but those silicon sides should be durable enough to handle whatever heat might dissipate up the sides.
It looks like the external dimension of your Heat Exchanger ring is around 23cm. I've only tested up to 14cm (Heat Exchanger) pots but there's a correlation between pot base size and distance to pan from burner. For a 23cm pot my results from smaller pots would indicate that you would get a fastest boil at an excess of 60mm distance. It looks like you only have a distance of around 20mm. There should be a significant improvement at 60mm and distances (mm) slightly beyond. Other tests with non-Heat Exchanger pots exhibit the same correlation.
I asked the question because from my experience your spacing looks far too close and wondered if you had done comparative tests at a greater distance? Mine have all shown that significant time savings can be made by adjusting the burner to pot distance and timing the result rather than looking at the flame.
Your burner and pan should easily achieve a 4 minute boil of two cups so if you're already near that time then your setup would seem to work OK. What time are you actually achieving?
In setting the optimal distance you will find that closer will have a longer boil time, extending the distance to the optimal will improve it, then further extension beyond that optimal distance will increase boil time again.