Making a road trip soon and hauling a trailer back, according to tire size calc I will be off by 3.5%... good tread left on my existing Duratracs, should I spend the $100 and get a same sized spare mounted? I would like to upgrade all wheels, tires and 2 spares (stock wheels used for spares, currently running '06 Tundras) later when I do the TBU so I'm hoping to not invest $$$ in something I will not be able to use later.