OK people, some news here: After long research i dropped the concept of DIY silicone molding and plastic casting because it appears too complicated, requires a lot of additional gear, results are not always predictable, and experiments may take many months. Also i find that those plastic casting materials are not too heat resistant and can deform under extreme sun. It is also problematic to get a neutral deep black color with them. So i return to concept of 3D printed box. I tested few different FDM 3D printers and find that they can produce very different results depending of used material and printer brand. Also instead of unpredictable fragile ABS plastic i find Elastan D70 - new industrial material developed by local manufacturer. It is solid but same time slightly elastic and resistant to impact loads (95 Shore Type D). Usable in temps from -40 to +120 °С. Resistant to UV light, X-ray, wet, oils, fats and many solvents, safe for food contact, low shrinkage durable material. Internal part of the box was also redesigned. It became much stronger now. In day or so i'll get a first test sample of printed box so we can see how it looks, how it feels and do a crash test with heavy hammer.