This is my first (gravel) bike build ever, so maybe I’m overthinking things a bit. What’s your impression of the general frame quality compared to large OEM frame sets? The price-performance ratio looks very good (I’m a composite engineer in the aviation sector, so yes… I tend to look at things a bit too closely).
That said, when I look at the wall thickness at the canvin aleous handlebar tube end, I’m not entirely sure I want to bomb down rough gravel at high speed if I can’t even mount the right lever properly (see attached pictures).
I stopped tightening the RH lever clamp bolt at 6 Nm (using carbon paste between clamp and bar). The lever is still slipping, which doesn’t exactly boost confidence.
Now I’m wondering whether the RH tube (if the wall thickness variations continue internally like at the visible tube end) might have suffered some local damage or even slight delamination. The small cracking noise I heard while loosening the bolt for readjustment didn’t exactly calm my nerves either. However, when doing a full push-down load test by hand on the handlebar, there is no noise or cracking, it feels solid and stable.
Maybe I’m just being overly sensitive — or maybe my engineering brain refuses to switch off.
Any thoughts?

A cracking noise seems suspiciously like delamination, but Google is telling me the lever torque should be 6-8Nm, which is within spec.  What does Assisting Force say?

As for the variations at the end of the bar, measure the tube wall thickness with calipers.  I have a carbon seatpost that looks like that on the end and it's just tapering within the last few mm.  The wall thickness is consistent.

Frames always ship with plastic tubes sticking out the cable ports, but they are not use to route naked cables.  The are used to help fish cables and housing through the frame.  You shove a cable through the guide until it sticks out both sides.  Then you remove the disposable tubes and feed the permanent housing through the frame by engulfing the cable as it goes.

Yes, Wing shared it with me, along with some other helpful info I requested:

I was interested in seeing how well they preserved some of the original geometry with the 120mm option.  They claim the same HTA and STA, and a 35mm BB sounds low for an XC bike, but still reasonable.  However, the fork axle to crown is 520, which is more like a 110mm fork.  Put a 120mm (or even 130mm) fork on there and the BB drop is going to be even less.  The FM1001 BB drop is only 28mm, which is low for even a trail bike, but I have not seen any complaints yet.

Are official geo measurements for the 936 available with the 120mm rear?

From drawings 909 has bit more clearance than 936. When I get my 909s I can check it thoroughly.

Did you receive your 909 yet?

Wing at Carbonda sent me these dimensions for FM936 and FM909 frames.  They list some dimensions around the tire area for both seatstays and chainstays, but most of the widths are missing, and it is unclear what the clearance is expected to be above the tread.  Wing said the standard is to allow for 6mm of clearance to the tire, which is where their max widths come from.

2.35" = 59.69mm
2.40" = 60.96mm
Diff  =  1.27mm

Has anyone used offset bushings with Carbonda 936 or 909 frames?  I just became aware of their existence, and the point seems to be to shift the shock in one direction in order to change the head angle and BB height. 
https://www.offsetbushings.com/pages/how-they-work

If the seat stays are pushed back, then you may have that many more mm of travel available before the bridge connecting the stays contacts the seat tube.  This could be one way to safely get >100mm travel out of either frame, but it would involve raising the BB and steepening the head tube.  This is the opposite affect that most users will want when using offset bushings in general.