Rick,

We made three sizes. 12''x15'', 15''x48'' and 24''x60''. The smallest one only had rubber feet and no aluminum. The middle size only had two parallel aluminum tubes. We never had any problems with the short direction on that one so we never put any cross pieces. The largest size, which is the picutre I attached above, had three cross pieces between the two parallel long tubes. These were just butted together with no actual connection. The idea there was again to allow the whole thing to be able to shift as the different materials expanded and contracted.

Todd