Workaround: disable the default scaling and adjust the font and minimum size

        Me.RadRadioButton1.Font = New Font("Arial", 12, FontStyle.Regular)
        Me.RadRadioButton1.ButtonElement.CheckMarkPrimitive.MinSize = New Size(20, 20)
        Dim radioPrimitive As RadioPrimitive = Me.RadRadioButton1.ButtonElement.CheckMarkPrimitive.FindDescendant(Of RadioPrimitive)()
        radioPrimitive.MinSize = New Size(21, 21)

    Public Class CutsomRadioButton
        Inherits RadRadioButton
        Protected Overrides Sub ScaleControl(factor As SizeF, specified As BoundsSpecified)
             
        End Sub
    End Class