TScrollBox with dynamically created Memos issue

Question

On my form there's a ScrollBox. I populate it with 2 dynamically created Memos like this:

 TotalHeight := 0;
 NewMemo := TMemo.Create(nil);
 NewMemo.Parent := ScrollBox1;
 NewMemo.Left := 0;
 NewMemo.Top := TotalHeight;
 NewMemo.Lines.Text := Memo1.Lines.Text;
 NewMemo.FitHeightToContent; //SEE BELOW !!!
 TotalHeight := TotalHeight + NewMemo.Height;

 NewMemo := TMemo.Create(nil);
 NewMemo.Parent := ScrollBox1;
 NewMemo.Left := 0;
 NewMemo.Top := TotalHeight;
 NewMemo.Lines.Text := Memo1.Lines.Text;
 NewMemo.FitHeightToContent;
 TotalHeight := TotalHeight + NewMemo.Height;

 ScrollBox1.VertScrollBar.Range := TotalHeight;

FitHeightToContent procedure code (taken from SO):

procedure TMemoHelper.FitHeightToContent;
var
 DC: HDC;
 SaveFont : HFont;
 Metrics : TTextMetric;
 LineHeight: Integer;
 Increase: Integer;
 LC: Integer;
begin
 DC := GetDC(Handle);
 SaveFont := SelectObject(DC, Font.Handle);
 GetTextMetrics(DC, Metrics);
 SelectObject(DC, SaveFont);
 ReleaseDC(Handle, DC);
 LineHeight := Metrics.tmHeight;
 Increase := Height;
 LC := Lines.Count;

 if LC < 1 then
      LC := 1;

 Height := LC * LineHeight + 8;
 Increase := Height - Increase;
end;

Memos have their word-wrap as false. Their height is such that if one memo is fully visible, the other's got only about 1 line of text visible.

THE PROBLEM: when I click on NOT fully visible memo, the scrollbox gets scrolled up or down to show the clicked-upon memo in full.

I experimented with memo sizes and problem persists. With different memo sizes this strange scrolling is different and not always fully exposes clicked-upon memos.