Well. A glass patch adds the strength back in tension, and is invisible in the finished camper, and doesn’t take any longer. The cement block is merely a flat weight to provide clamping pressure. Nonetheless, since panel 4 doesn’t bend much anywhere , you should be good to go. If you have any trouble with the glue, just take it out and do a glass patch. Only the builder knows about these gremlins; everybody else will admire your teardrop.