Whoops. Just noticed that you asked about HM 2, not 3. My bad. The HM 2 images are created as screenshots on my 2560x1440 monitor. Doing that I don't get anything quite as large as my HM3 characters, but pretty large. Using that technique I can create a 21st century Bette that is 719x1181, about the size of 800x1200 HM3s, the third largest size. I have combined them in composites create with Photoshop.
In the full history image the characters are smaller than that because I did them on a smaller computer (I think it was my 1440x900 laptop. Not sure, though.
My biggest HM3s are about 1461x2152 (21st century Bette).