Taking a look back at the gussets currently available it seems like some stronger ones would be of use. For example the Angle Gusset is made of weaker metal than the normal flat plate or anything else.
You can always make your own. We have gotten pretty proficient at making what we need from the various existing parts, particularly the flat plate.
We’ve used the ends of pieces of chassis rail as gussets but sometimes it would be much nicer to have something a bit better. The size and shape of the current gussets seems fine, however they are not all that strong.