select that specular and import the blank DDS it should be fine even if it's a different size.
I tried that and this is what I got:
The Sims 4 Studio - Version 2.5.0.2
Gibbed.Sims4.TextureCompress.RLEImageException: Exception of type 'Gibbed.Sims4.TextureCompress.RLEImageException' was thrown.
at Gibbed.Sims4.TextureCompress.RLEUtilities.ImportToRLE2(Stream input, Stream output, Endian endian) in c:\Workspace\Sims4Studio\TheS4Studio\S4Studio.Data\Rick\TextureCompress\RLEUtilities.cs:line 456
at Gibbed.Sims4.TextureCompress.RLEUtilities.ConvertDDS(Stream input, Stream output) in c:\Workspace\Sims4Studio\TheS4Studio\S4Studio.Data\Rick\TextureCompress\RLEUtilities.cs:line 102
at Gibbed.Sims4.TextureCompress.RLEUtilities.ConvertDDS(Byte[] src) in c:\Workspace\Sims4Studio\TheS4Studio\S4Studio.Data\Rick\TextureCompress\RLEUtilities.cs:line 60
at S4Studio.Data.IO.Images.RLE2ImageResource.set_DDS(Byte[] value) in c:\Workspace\Sims4Studio\TheS4Studio\S4Studio.Data\IO\Images\RLE2ImageResource.cs:line 37
at S4Studio.Data.IO.Images.RLE2ImageResource.set_RawImageData(Byte[] value) in c:\Workspace\Sims4Studio\TheS4Studio\S4Studio.Data\IO\Images\RLE2ImageResource.cs:line 49
at S4Studio.ViewModels.Warehouse.WarehousePackageViewModel.ImportResource(String f) in c:\Workspace\Sims4Studio\TheS4Studio\S4Studio\ViewModels\Warehouse\WarehousePackageViewModel.cs:line 406
at S4Studio.ViewModels.Warehouse.WarehousePackageViewModel.<.ctor>b__11() in c:\Workspace\Sims4Studio\TheS4Studio\S4Studio\ViewModels\Warehouse\WarehousePackageViewModel.cs:line 149
at S4Studio.ViewModels.GenericUserCommand.Execute(Object parameter) in c:\Workspace\Sims4Studio\TheS4Studio\S4Studio\Commands\GenericUserCommand.cs:line 22
at MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated)
at System.Windows.Controls.Primitives.ButtonBase.OnClick()
at System.Windows.Controls.Button.OnClick()
at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
at System.Windows.Input.InputManager.ProcessStagingArea()
at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)