Weddingbee boards

I would add a stiff horsehair ribbon inside the bottom of the hem. 

Perhaps two layers of it.  Perhaps one layer near the bottom and then two on top of each other at the very bottom.  I would have to play with it.

Or I might substitute some stiff netting.

Ask the alternations gal at the store to show you some options.  If she doesn't know what I am talking about, she has limited skills.

Try a tuxedo store that does alterations.  They'll know for certain. This stuff is used all the times in men's suit jackets, especially high end ones.  Plus they might have better ideas like stiff underlining and netting. 

Don't go to a cheap tuxedo store.  They won't have a clue.

Good luck!