Modifications to the plans and improvements (at least in my opinion).
Rivnuts
According to a Kitplanes article, Loctite has almost no effect on the force required to spin a rivnut, while super glue can at least double the force needed. Therefore, I recommend using super glue instead of Loctite to secure rivnuts. More insights in this Kitplanes article.
Engine
Fuel Lines
The fuel and water lines have been modified. I replaced the existing “garden hose” hose clamps with steel self-adjusting clamps, which are also used by Rotax. The heater hoses require clamps with a 14 x 25mm outside diameter, while the engine coolant hoses need clamps with an 8 x 32mm diameter. The fuel lines were replaced with steel braided PTFE lines, and I used corresponding fittings. The fuselage-side fuel lines are now all made of aluminum, and I have optimized their routing. For more information, please refer to the link provided. More info here: Fuel System
Coolant System
If you live in a colder climate, such as Germany in the winter, I would recommend using the Rotax water thermostat to prevent the engine from becoming too cold and to speed up the warm-up process. This can be helpful even during the summer months. Parts are available from Franz Aircraft Shop . You will also need about 50cm 25mm coolant hose for the radiator bypass. (suggested by my Sling distrubutor: Frisian Air )
Fuselage
Brakes
I upgraded to the stronger dual caliper Matco brakes. More info here: Landing Gear
Firewall Strengthening
Upon closer inspection behind the fuel filter, I noticed a slight flex in the firewall. To address this, I reinforced it using an additional spare c-channel, which also functions as a holder for the fuel line.
This USB port works with Apple devices and does not get hot when charging two iPads at the same time. I also checked for radio interference with a handheld receiver and fond none.
78W PD 3.0 USB C and A 
GTP 59 Replacement for €25 (EF9T-PT500-3L-4.0-W @ https://www.sensorshop24.de)
Air Vents: Fresh air will be supplied by the metal Aveo AirMaxi AVE-BMBLK-200 vents:
