OK - Thanks. Yes, this site is very useful indeed.
By the way, after I had written my last post, I remembered the printed Stars! manual that came with the boxed version and was buried on one of my shelves. :-)

Please confirm that you run Stars! under DOSBox For Windows (3.11) fullscreen on a 1920x1080 monitor without black borders on the left and right of the proper Stars! display.
I use the same conf parameters on my 1600x1050 monitor (and have also tried a 1600x900 monitor) and have never managed to get rid of the black borders (which is one of the reasons why I prefer to run Stars! under WineVDM).
Which parameter exactly do you think is causing the blackborders to vanish? It can't be aspect=false because I'm using this setting, too. Or is it possible that your larger monitor resolution makes the difference (I can't try it, because my monitors don't support your resolution)?

Confirmed.

Most likely thing I can think of is that you may have "aspect=true" set in the [render] section.
But if that's not worked for you it may possibly be something in the [sdl] section. Or maybe the "scaler" type under [render].
I can't think of anything else that would alter the display output.

The specific res of your monitor(s) shouldn't matter tho, dosbox should scale it match for fullscreen.

Thanks - I'm using exactly the same conf parameters as you (including aspect=false). Moreover I tried various scaler settings - no change. I even tried to run Stars! under DOSBox 0.73 to rule out version problems (normally I use 0.74-3).
In terms of size and shape the fullscreen and the windowed display are exactly the same, except that the window border is replaced by black borders covering the remaining monitor space to the left and right of the screen (the window covers the screen vertically).
Well,it's not a serious problem - Stars! uses the full screen in WineVDM, and I could live with the black borders, too.

It shouldn't make a difference, but I am using a frontend for dosbox I ported over from an old system.
Specifically a (probably out of date) copy of D-Fend Reloaded v1.4.2 which has its own pre-packed version of dosbox (which is reporting v0.74).

If nothing else it gives you all the possible options for any given params in dropdown boxes which makes experimentation a little less tedious.
I'm sure there are many different 'frontends' to choose from all of which I would imagine behave similarly, so if you do decide to investigate further this might be something to consider.

I recommend the DOSBox Game Launcher frontend paired with DOSBox ECE. The latter is a version of DOSBox that has received various upgrades, such as Roland MT-32 support. The Game Launcher can be set to use a DOSBox of your choice. Both are still being maintained, so you should be set for awhile.

Thank you for providing the package. I have never played the game before, but it looks interesting. The interface takes some time to get used to, but I think I will spend a good time with this title.

Thanks guys. I know D-Fend, and I'm used to edit the conf file - no need to use a front-end.
ECE appears to improve sound and joypad usage. I may have look when (if) I try to emulate Win98 with DOSBox.
Something is preventing aspect=false to work for me (I tried it on 2 PC's meanwhile). Instead of changing the aspect ratio, it simply adds black borders. Could it be graphics card related (I have an integrated Intel card)? It's unlikely that DOSBox itself works differently on different PCs, I guess it must have to do with properties of the PCs themselves.