For the bars I've used small carbon tube. My advice for cutting this is to use the edge of a small half round file and work around the circumference. Other methods can lead to splintering.
For the connection points I've used Caldercraft vine eyes
I made the bottom stay brackets twice as they were too big initially and my final version is still oversize but as small as I can manage.
I used styrene T section
I'd rather correct things in progress until I'm satisfied.
I use a 0.8mm drill and 1mm tap
From yesterday, the black ring in place
Nav light boxes in progress