I'm not sure I understand the question. The physical size of the screen has nothing to do with it. Because of that, Aces High would run just fine on any size screen.. heck you could probably hook it up to a jumbo-tron if your video card would support it!
Now the pixel count is a different matter but again there is no limit to the number of pixels Aces High will run on. Your limitation as far as that goes is how good your video card(s) are.
It is a common misconception that larger monitors have more pixels. This is actually not normally the case. Especially since High Definition standards have come into play on televisions, computer monitors (for the most part) match those standards. Yes there are exceptions but not from the 'economy' options available at your local retailer. Simply put, most larger monitors have the same number of pixels as the smaller ones but the physical size of each pixel is larger.
If I take my 24" computer monitor which has a resolution of 1920X1200 and compare it to my 47" television (technically a monitor as well because it lacks a tuner) which has a resolution of 1920X1080, then in my case my smaller monitor has more pixels than my larger one!
Again, to more clearly answer your question, there is no limit to the physical size of the monitor required to run Aces High II.