National RV 2003 Islander

The early ones were built on a DynoMax chassis. What National did was have Country Coach cut holes in the frame tubes and then weld gussets on either side. The holes in the frame is where the slide mechanisms run through. It does weaken the frame and during a situation where the chassis goes over some really uneven ground such as a speed bump,the frame can twist. If there are mirrors on the wall behind the front slide, the slide can twist the frame enough that allows the slide wall to break the mirrors. I have seen this happen.