Add arrowhead to shape layer using trim paths & expressions?

Hi,

I am trying to use expressions to attach an arrowhead to a shape layer.

I'm using the 'trim paths' effect on the shape layer to grow a stroke over time (using the start/end/offset features).

I would like to attach an arrowhead to the tip of the stroke, using an expression to animate it dynamically (e.g. the arrowhead follows the stroke when animated using the start/end/offset values)

I've attached a basic project file if anyone can help?

94_shapelayerarrowhead.zip

Thanks for your time, any help appreciated

Tim