Great tool, but lose it on dark pages Rated 4 out of 5 stars

I love the MeasureIt tool, and use it frequently. I have two issues that I'd love to see fixed (or explained what I'm doing wrong):

One is that I lose the crosshairs on web pages with a dark background. I'd love for the tool to automatically turn white or yellow or red or some easily see-able color on dark pages.

The other is that I find that the boxes are not re-sizable. I thought they used to be. Can that be fixed?

And a feature request: It would be great to be able to specify an exact size so that I don't have to struggle to drag a box of a certain size. Additionally, it would also be useful to be able to specify one dimension, but let the other be changeable when the box is drawn.

Thanks!

This review is for a previous version of the add-on (0.4.10.1-signed). 

That's a great suggestion. Thanks jandreasen!