Sorry, didn't read your post properly the first time, so that I actually missed that you have a 16:9 monitor.
You could use [-] (and [+]) key of numeric keypad to adjust size till it fits your monitor.
Also using numeric keyboard keys [8] / [2] you can move screen up / down (and [4] / [6] to move left / right, but that is of less interest to you) Numeric [5] will just "reset"
P.S.
Options to "Remember Pan-Scan settings" (and "Remember window size" if not in full screen mode) could be of interest to you
(under rightclick > Options > Video > General)
(Perhaps also have a look at
these posts)