There are a lot of issues to consider. Basically, most of the testing is to find an EI and not the film speed. As such, you really don't need to be precise, but to do any kind of proper testing, you need to understand what you are testing for and the variables and conditions involved. A beginner creating thier own testing procedures really isn't the most practical approach. You're attempting to reinvent the wheel without understanding what it is.
Originally Posted by sewarion
Ten subject Zones equals ten stops or a log luminance range of 3.0. Glossy paper has around a maximum of log 2.0 relectance range. Matte paper has less. If you want to use your own scales, have them measured and use those measurements to compare with the finished print. Personally, I would recommend testing the film using a step tablet, and don't get caught up thinking only in Zones.