Quote:
...but the window always starts really small or short and it gets annoying having to drag the window each time to zoom...
It reads to me like you are using traditional 3 window mode.
Strongly recommend going into single window mode Gimp menu
Windows -> Single window mode and using Wallaces suggestion.
Other thing to try
In 3 window mode set
Edit -> Preferences Zoom and Resize Behaviour
screenshot:
http://imgur.com/PyWubwhThere are preset shortcut keys for zoom, 5 = 1600% and there are a couple of unset options that might get you larger than that screenshot:
http://imgur.com/rq4MpIgA non-gimp, linux option depending on the DE you use

look for forcing a window size when opening an image.
screenshot:
http://imgur.com/Qq5WJaQthen apply a shortcut to zoom.