ASCP - Are Supplier Capacity tolerance fences considered when running an unconstrained plan.

 I am running an Unconstrained ASCP plan, with Supplier Capacity and Calendar details entered. 

Although the supplier capacity is not itself a constraint ASCP does in fact issue exception messages that the Supplier capacity is overloaded, based on accumulated available capacity and Requirements.

I am now trying to also get the Supplier Tolerance fences to work, and be considered when calculating Available capacity, but do not get any result - only the base capacity is used.

Does anyone know if 'Supplier Capacity Tolerence Fences' are only considered when running a Constrained plan, or if there is some set up / profile i have missed.