9inch silent long range

I decided to work a little bit on my older concept of the pyramid tubular frame, this time reworking the joints, optimizing weight by using smaller support tubes and creating snap-on aerodynamic canopy which houses Camera/VTX/RX.
I'm very pleased with this 9/10inch frame, some stats:

• 86g bare frame weight, 104g complete weight including canopy with snap-on fittings
• 581g weight of the complete drone without battery, using GEPRC EM2812 motors and Gemfan 9x4.5x3 propellers
• Happymodel diversity 868mhz elrs RX
• Speedybee F405 AIO (40A per channel ESC, while the motor/prop combo has current draw of ~36 at max throttle)
• Skyzone 2.5W VTX
• Runcam 2 Pro camera
• TrueRC vtx antenna
  Here is the video of first short test flight, with small 1050mah 6s battery (180g, so around 760g complete weight) -
  
  I'm using UAVTech 10" preset (clean build, so minimal filtering), which is meant for 1400-1700g AUW with 3115 motors and is clearly not optimal for the drone with half the weight -> you can see that it's little bit wobbly, especially when just hovering or moving slowly, better when going fast - but it was also super windy and the drone has very low disc loading with the small battery, so that's a factor as well.
  The same preset worked very well when the frame was used with bigger 3115 motors and much heavier 800-900g battery.
  My plan is to use 3000-4000mah lipo (400-500g) for the final weight of bit over 1kg, I will than adjust the preset to better fit the lighter weight.
  Efficiency is phenomenal, 3minutes of flying took ~410mah from the battery and that was in chilly conditions 2-3C above zero.
  I expect to achieve 20min flight time with 3300mah 6s lipo with normal flying (mostly cruising, couple of punch-outs), but let's see.
  Another thing which surprised my a little bit is how silent it is -> I was testing 5inch drone on the same place previous day (the small green one in the photos) and it was much, much louder, this one hovers at 13-14% throttle and I could barely hear it 20-30m away in windy conditions.