The Lack of strength of the top of the guards was likely due to the PETG sagging a little? More heat+fan my have given a better result? The added weight of 3 lines would be well worth any extra weight in my opinion and there is plenty of clearance to the motor to go inward with the 3rd line. PETG does generally have very good layer adhesion and the rest of the print seems good. I have resisted purchasing any Nylon for now as we are coming into the wet season, the Humidity is very high and I’m working ‘outdoors’ (open carport).But I think to design around PETG does give more of us the ability to reproduce your efforts.
A rough measurement shows approx 1mm between arm struts to the rear and 1.5mm to the front, A Generous 2mm would allow the wires to sit neatly with 2 below and 1 above.
The board in the picture is one of Charlie’s F4 Alienwhoop DIY boards. When I do get around to ordering the parts and attempting assembly I will certainly consider converting one to brushless and dedicating it to one of your frames.
Regarding Flex, While I would not quite put the frame in the same stiffness category as CF, my PETG frame feels as though the thrust of 0703 motors on 1S would not cause mach concern.
The motor mounting plates appear to be 2mm? This I think could be reduced by 0.5m or so to give better grab to the stock screws, or perhaps a motor screw recess could be incorporated into the first layers? As could a bearing recess be incorporated into the upper couple of Layers ( easy enough to do later with a drill bit).