Knowledge Base (Overview: Materials in Microvellum) notes "If all sheets have an optimization priority of 1, the system will optimize to get the best yield using all the available sheets. Numbers greater than one will optimize as materials are needed."

I have 3x parts which require a 3.1m board instead of 2.4m. My 2400 sheets are at optimization priority 1 while my 3115 sheets are at optimization priority 10. (tested at 2, 10 & 100, as well as at 1 with matching results for all)

For each test, parts that would easily fit on 2400 board were nesting on my single 3115 sheet while the 3x parts that needed to nest on the 3115 failed to nest.

Does optimization priority for sheet stock work at all? It definitely doesn't seem to work as the above link notes.