The K-4 is not bad, but there are a few items that need addressing.
1. You need to fix the colors on the prop spinner. On the AH 109 bitmaps, the rear portion of the spinner is on the fuselage parts. You need to paint those areas black or RLM 70 (Don't worry about continuing the white spiral, those were rarely painted on the backing plate on real 109's)
2. Continue the yellow nose band under the nose. This was an IFF marking and having it visible to ground gunners was even more important than for other aircraft. Also, darken the color to reduce the level of glowing.
3. The fuel filler cap and triangle stencil need to be moved forward into the next fuselage section. Also, the Blue 7 needs its placement moved forward, with the fuel grade stencil overlapping the upper left corner.
4. Enlarge the fuselage crosses so that the width fully spans between the panel lines in its section.
5. Add the opening in the cowl for the exhaust pipes. This area is a rectangular hole for all of the exhaust stacks. The top should be angled downward to the rear to match the upper exhaust shroud piece.
6. Add the lower cowl bumps. The G-10 and K-4 had wider engines than previous 109's that necessitated widening the front of the lower cowl. This was achieved by adding teardrop shaped fairings.
7. Add cooling scoops to the forward cowling. Beginning with the G series, all 109's had a pair of scoops added to the front cowl on each side. The rear scoops are slightly higher up than the forward set.
Here is an image from my K-4 template to illustrate what I'm talking about.
