cometguy

I have a 2015 Panamera 4 and have ordered a 2018 Panamera 4 ST E-Hybrid, both with 19-inch wheels.
I want to take these on long trips, so want to get a new front wheel/tire to keep in the back for cross-country trips where I may be far from Porsche Road Assistance.
Do any of you guys know if there is any reason why I could *not* use a front "spare" as a rear wheel/tire in an emergency, for up to one or two hundred miles? Would the brakes be affected at all for a rear wheel, given the less-wide front tire?

Thanks for any input you can give me on this.