Thank you for the fast response!
I don't plan to use such a tiny text size, I used it as an extreme example to illustrate the extreme differences in text sizes in order to determine if a search engine would care.
The H1 tag's text size would make the style of my page look awkward. That's why I want to reduce it. But I also want the boost the H1 tag gives to the words in the heading.
So, since the answer is that reducing the text size won't confuse the search engines, then I will use the H1 tag, but I will reduce the text size so that it matches the style of my pages.