I killed my first mangrove... I knew pinching this one was risky given that it only had a single set of mature leaves. It did try to push out another shoot from the base, but I think it doesn't have enough energy... 
Pre-Bonsai'ing
Bon-dying
But the other two I bonsai'ed are doing well! Both are pushing out new shoots...


Pre-Bonsai'ing
Bon-dying
But the other two I bonsai'ed are doing well! Both are pushing out new shoots...

I guess you could try just cutting out a hole in the back of the canopy/lid to let the mangrove grow through.
Very cool set up.