Good luck with mismatched tires.My son was rushed to the emergency room last year and admitted to intensive care in extremely critical condition and I HAD to replace my front tires right now to get out there.There were no new front tires available I could get that day.My buddy at Discount Tire found me a set of used Michelins (140mph rated)to throw on the front and with my new Nitto Motivo's on the rear.
Recently I did a Rte 66 crawl to Chicago and back,around town the combination of Michelin's with the Nitto's was okay,at 65mph they were okay,at 75 they got a bit darty,at 110 they were getting snakey,at 140 they were a white knuckle handful,after almost a half an hour at 140 I was glad to slow down to 110 again.
BTW,the 110 and 140 blasts were this May on Memorial Day week end on the Interstate in the middle of nowhere with no other traffic out there.