This side curtain is not original equipment style for the MGA 1500, but is a common replacement type similar to the factory style 1600 side curtains. The rubber seal around the top and back edges make it a pretty good fit against the fabric top. Notice that the side curtain rests against the outside surface of the outer fabric flap around the side opening, all around except for a few inches at the front.

An aluminum side curtain without a rubber seal around the top is possibly a factory style side curtain intended for use with the factory aluminum hardtop. That type of side curtain was often provided by the dealers as a replacement for the original 1500 style that were really impractical to use. I did once have a side curtain set without the rubber seal on the edge, and it did fit in under the outer fabric flap all along the top edge, but still not at the back.

The next view shows what you can do with the side curtains to improve your situation a little if you hit a really bad rain storm.