A way to avoid the problem of AeroSnap resizing windows when positioning them is to use a program called
Divvy. When called on, Divvy puts grid on each monitor; you can predetermine the number of rows and columns on the grid. You then drag an outline on the grid and, when you release the mouse button, the active window will automatically move and resize the window to the position and size indicated by the grid. I mostly use keyboard commands for AeroSnap when full or half screen is good enough for me and Divvy when I need finer tuning of window size and position. Divvy has a free trial version that is full featured but can be used for free indefinitely.