I'm wearing it with nothing on underneath in the picture there (and the three following) and it closes neatly in front, the silk even overlaps. I think that once I have the proper stuff on underneath it will still cooperate.
So, at this point, if I hem it the gown is ready to be worn. The guarding I can add at any point now, as I just stitch it down ontop. I have no hook/eye pair on the sleeves, but the opening is rather short, so they stay closed. Probably with a chemise sleeve they might gap and I'd need the closing. So I shall add those right now. Unfortunately I do need help with hemming, so I can't finish it /before/ the event. But I may be able to do it on site. If I so choose.