The default templates for the marker and needle do not support using the BorderThickness property.
The tooltip from the control level does not appear on the scale.
The scenario is very simple. Data range for the gauge could be very different, so we can set some hardcoded values for the min and max properties. Now we for the min and max we set minimum and maximum from our value, but in this case we have not very beautiful labels, i.e. 90 is min and 165 is max, we show 10 labels so labels are 90, 98,33, 106,67 etc.
The Gauge control should allow to override the whole entire "Content" property of the tooltip like to the ItemToolTipOpening event of ChartArea. Declined: Duplicate with http://feedback.telerik.com/Project/143/Feedback/Details/113231-gauge-add-ability-to-override-the-content-property-of-the-tooltip