Looks good Adrian, but a bit big for me coming from a 13cms perspective 
And did you do the RF absorption test on the plastic tube? At 23cms shouldn’t matter much and if it is performing as well as your J Beams - then it’s-a-working! I had problems with my 13cms 21el design in that the plastic tube (sample) I had intended using for the boom was heating up in the microwave. Abandoned this for a fibreglass tube section of one of my old SOTA poles. Did the microwave test and all fine with this.
Interestingly, later I was testing the glue I intended to use to secure the folded dipole. It appeared to heat up in the microwave. I suspected the cardboard I had used for glue sample. Tested the cardboard on it’s own. Sure enough it heated up. Tried the glue again on a piece of fibreglass. All ok!
Shortly I’ll put some pics on this Reflector as to the SOTA make-up of the beam (SOTA friendly (no need for a tripod) - same idea as with the SG Labs 4 el pcb yagi with the hole to accommodate a SOTA pole as you can see in this TOPIC). And a more detailed explanation on GM13 to follow.
73
Jack(;>J