Overriding width of button does not work as it should

[Cyerus]

Environment

• Fluent.Ribbon v3.6.1 / v4.0.0-beta
• Theme All
• Windows 10
• .NET Framework 4.5

I'm trying to overrule the default width of a button, but I'm not having much success.
It seems the length of the text is leading. However, I would like to overrule this behaviour by setting a fixed width, so that buttons with less text (less width) can be set to the same width as buttons with more text.

Considering the following example;

<Fluent:RibbonGroupBox Header="Group" Height="84" Width="500">
    <Fluent:Button Name="buttonGreen" Header="Green Long Name" Icon="Images\Icon1.png" LargeIcon="Images\Icon1.png" Width="100" />
    <Fluent:Button Name="buttonRed" Header="Red" Icon="Images\Icon2.png" LargeIcon="Images\Icon2.png" Width="100" />
</Fluent:RibbonGroupBox>

I have 2 button-areas, both set to 100 width. One with a large header, the other having a short header. However, each actual button inside this 'buttons-area' is smaller.

Is there any way to change this behaviour?