I need some modeling help ...

The original polygon was number two. I tried to uniform scale extrude face but it was going over into the instanced mirror so I just scaled it up in one direction.

I wanted it wider though, so I extended the edge to make polygon labeled one, now I can have four rocket launchers, two on each side

I then selected both polygons and extruded face but it goes all wacky anyway I try it, usually in polygon number one, the edge extruded on.

If I try and extrude polygon number two by itself it is ok but polygon one, the edge extruded one, seems not to like it ... it seems to have multiple edges arounf it and I can not even seem to merge them

How can I fix this