"vboxsdl --fullscreen" and RandR settings

[frac]

I've configured a WinXP VM that runs automatically (via "vboxsdl --fullscreen --startvm WinXP") when the system comes up.
It works nicely and resizes host's display whenever the guest OS changes the Screen Mode.

...But...

I've just realized that when the "--fullscreen" switch is used, it is impossible to change host's screen settings via "xrandr" command.

I need to display my WinXP VM on a top-down LCD display housed in a kiosk, so I tried to "xrandr -o inverse" the xserver:
the only way I've found to make it work is avoiding the "--fullscreen", losing the (vital!) automatic host's resolution change.

Is there any configuration parameter to avoid "exclusive RandR lock" by vboxsdl?
Do I need to patch the source?
I could syncronize guest's Screen Mode changes with host's "xrand -s WWWxHHH -o inverted" operations, but it would be tricky and unreliable...

Any better solution would be appreciated.
TIA,
F'

[Spadefinger]

Super necro bump for a solution. I know it's very rude. My apologies.

Please don't tell me to search for the solution because I am stupid. That's how I got here.

Please don't tell me to RTM, because the issue is not referenced in either manual as far as I can tell.

5 years later and this is the only reference I can find to my very current issue.

Please see the OP for a problem description. Mine is identical.

Host os Ubuntu 14.10 server. Guest XPSP3.

Thanks...

And sorry once again for the necro bump.

EDIT: Found a better manual for VBoxSDL.
I ended up using −−fixedmode instead of --fullscreen.
randr works fine with this mode.

Not perfect. But better.

Again sorry for necro, but hopefully it will help someone else.