I love seeing your various projects Bojan and they must be inspirational for many folk.
All I wanted to mention is making a camera container or whatever really, and I have done this many times, you can make it out of cardboard or balsa wood and then give it a couple of coats of fibre glass resin...you could add fibre glass but I use black tile grout...I am not sure if it adds to the strength which it doesn't have to really after a couple of coats of resin but it looks great...the other thing is on your last coat cover it with a nice paper .. just office paper and that gives a reasonably smooth surface that usually does not need much sanding...the paper soaks in the resin and then adds to the strength...
Adding paper is invaluable if you use fibre glass matt as it can be a pain to sand...also the paper is not paper anymore but plastic impregnated wood fibre
...to be convinced resin up just three sheets of paper and stick them together and note the strength.. same with balsa wood...resin up some thin stuff and observe how strong it becomes...I know you are into metal work but nothing like having fibre glassing ( or resin reinforced stuff) under your belt.
I have made a pier this way but used form ply.. resin glass and paper it was as strong as steel..or do I believe
Alex