The Face PlateI am still in the planning phases of my Gonk Droid, I began by adding expanding foam to the inside of my droid. My thought process is that since the tubs I have are (I believe) polyurethane, they are very flexible and do not stand up against sharpe, strong knocks. My hope is that the expanding foam will give it more internal structure.
I also plan to put styrene sheets around the outside of the gonk for even more structual support but also to make it easier to glue and paint. I did attempt to glue things directly to the tubs but it was very difficult to do this since the slightest movement of the tubs and it came straight off. Also I had to sand the tubs quite harshly to scratch them up enough to make a good bond.