I got a pair of the Nize Zoom Victory training flats about 10 days ago. I had been training in the Zoom Elites and had never had a problem.These new shoes are blistering the hell out of my achilles tendons. I've tried blister pads, gauze tape, tightening the shoes and can't seem to find a fix. I like the shoes a lot otherwise, any suggestions to modifying the shoe to alleviate the problem ?