Try this example code. Below is the aspx page with the silverlight control, and below that is the xaml code for the grid with colored rows. Notice that the grid has 8 rows of 100 height each, but only the first 6 rows show up. I can't get any control to show larger than 600.
aspx code
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<div>
<asp:Silverlight ID="Xaml1" runat="server" Source="~/ClientBin/x.xap" MinimumVersion="2.0.31005.0" Width="100%" Height="100%" />
</div>
</form>
</body>
</html>
XAML Code
<UserControl xmlns:my1="clr- namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data" x:Class="x.Test"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Width="400" Height="Auto">
<Grid x:Name="LayoutRoot" Background="White">
<Grid.RowDefinitions >
<RowDefinition Height="100"/>
<RowDefinition Height="100"/>
<RowDefinition Height="100"/>
<RowDefinition Height="100"/>
<RowDefinition Height="100"/>
<RowDefinition Height="100" />
<RowDefinition Height="100" />
<RowDefinition Height="100" />
</Grid.RowDefinitions>
<Rectangle Grid.Row="0" Fill="Green"/>
<Rectangle Grid.Row="1" Fill="Red" />
<Rectangle Grid.Row="2" Fill="Blue" />
<Rectangle Grid.Row="3" Fill="Orange"/>
<Rectangle Grid.Row="4" Fill="Yellow" />
<Rectangle Grid.Row="5" Fill="Black" />
<Rectangle Grid.Row="6" Fill="Aqua"/>
<Rectangle Grid.Row="7" Fill="Olive"/>
</Grid>
</UserControl>
Ideas?