With my 4S 5000mAh pack mounted as far forward as possible, I had to place about 2mm in shims below the front body mount to clear the body. I use the RCM battery tray mounted directly to the chassis and side guard. With a custom tray you could lower it a bit, but not much more. The 4s Flightpower pack is listed with the following dimensions: 35MM/44MM/166MM. If I had the battery tray about 2-3cm further back, I would probably not need the shims. But to fit a 53mm tall pack under the body without raising it might be pretty tough. The stock body fits pretty low and snug.