CAD files can be found here:
https://shrediquette.blogspot.com/2020/04/my-15-inch-long-range-setup-for-2020.html

This is my latest 15 inch ultra-long range setup with 50 minutes flight time:

• Propellers: 15x5.5" Tarot with custom hub
• Motors: T-Motor MN3110 470 kV
• Frame: 240g custom carbon structure
• Lipo: 2x 4S 4000 mAh SLS 20C (parallel)
• Camera: Micro Runcam micro sparrow
• Firmware: INAV
• FC: Holybro Kakute F7
• ESC: Tekko32 F3
• GPS BN-180
• Compass: QMC5883L
• Receiver: FRSky R9 slim+
  Hovering flight time is 50 minutes at 8.5 Amps and 40% throttle. Current goes up to 12 A when flying 50-60 km/h

Flight characteristics are really good when tuned properly (you'll nee a HUGE D-term). INAV 2.4.0 PID settings:

set mc_p_pitch = 85
set mc_i_pitch = 60
set mc_d_pitch = 150
set mc_p_roll = 85
set mc_i_roll = 60
set mc_d_roll = 150
set mc_p_yaw = 200
set mc_i_yaw = 70
set mc_p_level = 40
set mc_i_level = 10
set max_angle_inclination_rll = 500
set max_angle_inclination_pit = 500
set dterm_lpf_hz = 30
set use_dterm_fir_filter = OFF
set yaw_lpf_hz = 50
set dterm_setpoint_weight = 0.600
set dterm_notch_hz = 108
set dterm_notch_cutoff = 72
set rate_accel_limit_roll_pitch = 2400
set rate_accel_limit_yaw = 360
set heading_hold_rate_limit = 30
set d_boost_factor = 1.500
set d_boost_gyro_delta_lpf_hz = 40
set antigravity_gain = 2.000
set antigravity_accelerator = 5.000
set tpa_rate = 20
set rc_expo = 77
set roll_rate = 27
set pitch_rate = 27