I just submitted
#306 where the mark is 10% smaller than #242 for comparison..
You are right in exploring the options as it will affect other branding medium. I do provide both stacked and horizontal version of the logo.
In the case of business card, it depends largely on what information goes on it and how the designer arrange the layout. The size of the mark against the text in #242 and
#306 are quite common in general. That being said, If this design is chosen we can work out the business card at a small fee if you are comfortable with my style.
As for the truck door, if using only one door for the logo, a stacked version will allow optimum display as compare to horizontal version. But the design is bold enough to be displayed horizontally without losing its clarity.
Hope I have explain it well and feel free to ask me any other question that you may have :)