If I may, I believe cost is a concern to you as it is to most of us. So I will discuss that and the cheaper alternatives.
That metal hull sure is a neat thing to have but let's face it costs as much as the tank itself. If you mean to use steel wheels and tracks simply buy it that way and reinforce the hull. Another forum member posted a video of a tiger with a cracked on the hull and showed how he braced the frame to eliminate future cracks-aluminum bar brace across the hull top. He turns the tank over in the video to show something and what do you know, this tank with the cracks has a steel hull. Make of that what you will, the point is a plastic HE tank hull can be braced very cheaply. A steel plate transmission mount helps quite a bit, one can also be made using styrene sheet laminate while adding very little weight. Add a cross bar across the hull, preferably removable, plus maybe some styrene gussets wherever it looks like it will do some good, and you will have a more rigid hull With Less flex.

Many people also add styrene "ribs" in a box shape under the turret; it's heavy and this is a weak spot of the upper hull so every little bit helps. If it's done right the upper and lower hulls when joined become very strong, resist flex and perhaps less likely to throw a track or develop cracks later. The factory obviously isn't going to do any of this, so it's up to the modeler to mod the tank to eliminate it's weak points (re-engineering is most of the fun of the hobby, to me).