Strap up if you need to. Makes no sense to limit your back and leg development because you can't grip the bar. Proffesional toughman use straps. I use straps when I do reps and can still pull my max single when I want to. Use the straps. When your done deadlifting set the pins high in a rack and do a couple sets of static holds. Won't take long for your grip strength to catch up. I never use a mixed grip cause I'm not going to risk a bicep tear. I can pull 600 with a regular grip for one.