The manzanita is held together by its own weight and how it naturally rests on the bottom. I few small pieces I zip tied together. The only expanding foam used was in the construction of the base of the land areas. I lined the glass with plastic wrap, placed in the egg crate, laid down the weed guard and wrapped the weed guard down between the glass and egg crate, then foamed the edges. This created a solid seal around the edges stopping soil from entering the lower voids along with creating the pressure needed for the air circulation system to function properly. The other place I used foam was inside the cork logs that line the edges to hold them in place so they wouldn't float up with the water level.
High humidity isn't to difficult. Just give yourself plenty of variables. More vent then you think you may need that can be plugged or unplugged. Out of the six that I drilled I only use two. Variable speed fans for circulation. One thing to remember is as the tank matures and plants become more dense or with seasonal weather patterns come and go you may need to adjust things. I was fortunate with this setup that once I added LED's it was fairly simple to dial things in. It just takes patience and make slow adjustments over a longer period of time. Much like fertilizing a planted tank.
After this tank settled in. I only use two of the six vents. Circulation fans set at 7.5 volts, and the misters come on twice a day 8am and 2pm for 1:58. I maintain humidity here in Arizona at 80-85% with temps between 75-78. The front of the glass never fogs up. It takes very little fresh air from circulation drawn across the front glass for the glass to remain humidity free.