Indeed, the G-10 had pretty much the same performance as the K. The K was only speedier, by ca. 20-25 kph with it`s aerodynamic refinements.
The main difference between K-4 and G-10 were :
- large wheels are standard on the K-4, with fairings
- long tailwheel is standard on the K-4, and retractable
- tall tail also standard, with Flettner
- K-4 has redesigned, rationalized cocpit
- MK 108 standard
- internal arrangement of subsystems revised on the 109K, ie. master compass, radios, batteries.
- K-4`s MW50 tank can also be used as an extra fuel tank.
Both type had increased electronic capacity (2000W), shared to DB 605 D engine, and the associated wide blade prop (also true for G-6/AS and G-14/AS). Both of them received Flettner tabs for ailerons on occasion.