So I tried turning off "AllowMainCamera" and "CycleMainCamera" in the config files for a more difficult gameplay challenge, but found the mod's behaviour to be a little bit buggy like this.
For instance, when "AllowMainCamera" is off and "CycleMainCamera" is off, when cycling through the main camera, it comes up briefly on screen and then is immediately removed, resulting in an unpleasant flash. Furthermore, when hitting backspace to go back to the main camera, this glitchy flash comes up again, as the main camera is set, and the quickly unset.
Also, when "AllowMainCamera" is on and "CycleMainCamera" is off, you can actually cycle to the main camera in when cycling backwards (hitting equals), even though you've specified to not allow that behaviour.
So as not to come off as a complaining mod user to these fine mod making folks, I took it up myself to fix these bugs and give back to the thread.
I've tested for all cases when those flags are either on or off, in any order, and the glitchy screen flash bug is gone, and also when "AllowMainCamera" is on and "CycleMainCamera" is off, you now cannot cycle to the main camera in any direction, but can return to it by pressing backspace.
Here is the new dll file: https://dl.dropboxusercontent.com/u/53792213/HullCamera.dll
And here is the new source: https://dl.dropboxusercontent.com/u/53792213/HullcamVDS0.50-Constan7ineModification-src.zip
Thanks to Albert VDS for this mod, it's rather great, and I hope I've been a help to someone!