Nice to see your tank coming back.
Drill a series of very small holes ( just large enough for a needle to go through). Use nylon thread to stitch the crack together and then epoxy over top of everything ( even super glue would work, once absorbed into the nylon thread and hardens it is forever)
Only other option would be to make another brace and attach from the top but I think that would look like crap. Guess tank manufacturers don't sell replacement trim... That would really be the way to go, complete replacement.