No, size doesn't matter, but models would not go in my Australian list. Allow me to expand on this.
What I concentrate on are agricultural and industrial engines. The exception is marine engines. These are often sold in stationary format as well.
If we include all engines, we would have to include aircraft, car, motor cycle and tractor engines too.
My research files contain information on some of these, though not included in my engine list. After learning that there were Australian built model aero engines, I have added them to my files.
Here is another one to look at:
http://dkd.net/clmodels/bengines.htmlSo, though I would not put model engines on my list, they are definitely worthy of recording.
Eric