Why not use TUniRegionPanel component from PatMap:
http://forums.unigui.com/index.php?/topic/1233-region-slider-panel/page__view__findpost__p__4313
object MainForm: TMainForm
Left = 0
Top = 0
Caption = 'MainForm'
ClientHeight = 421
ClientWidth = 707
Color = clBtnFace
OldCreateOrder = False
MonitoredKeys.Keys = <>
PixelsPerInch = 96
TextHeight = 13
object UniRegionPanel1: TUniRegionPanel
Left = 0
Top = 0
Width = 707
Height = 421
Caption = 'UniRegionPanel1'
Align = alClient
Anchors = [akLeft, akTop, akRight, akBottom]
Color = clBtnFace
TabOrder = 0
Regionable = False
RegionSplit = False
RegionFrame = False
RegionTitleCollapse = False
RegionCollapsible = False
Region = rgCenter
object UniRegionPanel2: TUniRegionPanel
Left = 1
Top = 1
Width = 185
Height = 419
Caption = 'UniRegionPanel1'
Align = alLeft
Anchors = [akLeft, akTop, akBottom]
Color = clBtnFace
TabOrder = 1
Regionable = True
RegionSplit = False
RegionFrame = False
RegionTitleCollapse = False
RegionCollapsible = True
Region = rgWest
RegionParent = UniRegionPanel1
end
object UniRegionPanel3: TUniRegionPanel
Left = 185
Top = 1
Width = 522
Height = 419
Caption = 'UniRegionPanel3'
Align = alClient
Anchors = [akLeft, akTop, akRight, akBottom]
Color = clBtnFace
TabOrder = 2
Regionable = True
RegionSplit = False
RegionFrame = False
RegionTitleCollapse = False
RegionCollapsible = False
Region = rgCenter
RegionParent = UniRegionPanel1
end
end
end