Patient is coming home from rehab, severe mobility problems, requires rolling shower chair. Shower door threshold is about 3.5" above shower floor. Ramp on bathroom side is no problem, but ramp on shower side would take up most of stall floor. We want to find a plastic grid/mesh flooring naterial about 3" thick (or stackable to that height), tight enough mesh to accommodate rolling chair casters, that can be cut to fit the stall. Essentially raise the "floor" to height of threshold. Any ideas, sources of material, alternatives?