I've test it and it work as you say.
That was the good part. I continue with less good parts:
1. In .properties file you specified this:
- Export Plan to Image and version=1.0
That's mean it's a different plugin at first version.
(The last version was Export plan to image and version=1.0.3)
2. You've made a good addition with inch and cm BUT I suggest you to use the measure system set by SH3D.
Take a look at ShapeGenerator or TerrainGenerator how to do this.
I hope to not upset you.