Im planning to use short hair fiberglass to blend my new Peakes Dash to the steel frame. Will I be looking for trouble like cracking of the fiberglass since the metals expand and retract at different rates.
I would use a panel bond rather than fiberglass. Fiberglass resin needs physical adhesion, it does not stick to metal very well. It will crack eventually due to the movement in the dash.
I used their products in a production bodyshop for years without any issues. I glued doorskins, roof skins and 1/4 panels on with that stuff. I never had a recheck!! The glue is actually stronger than the spotwelds.