Hi Laszlo,
Thanks for using Syncfusion Products.
We need some clarification from you regarding "you use hack/trick for "AirSpace" issue on MDI. But it's still exists when an AutoHidden comes over to a WinForms control". Could you please explain your requirement in detailed to us?
But some prediction and we thought that you have faced our known issue in AutoHidden panel when it is used with WinForms. To resolve this known issue, we had specifically implemented "PopupAutoHidePreview" feature and if you have faced that issue means, please use this mentioned feature as "UsePopupAutoHidePreview=True". Here we have attached a simple sample with this feature for your reference.
Regards,
Muthalagu
AutoHiddenKnownIssueResolved_2692be30.zip