IoT 20mm rails for 3030 T-Nuts and 2020 extruded aluminium accessories

The classic 3030 is too large for IoT projects, and the 2020 T-Nuts are too frail when printed. These 20mm by 20mm and 22mm by 22mm extrusions are compatible with 3030 T-Nuts and 2020 accessories, but are smaller in size than the 3030 originals and they fit T-nuts with M4 nuts and screws, which classic 2020 rails wouldn't. 

Print tall rails with a brim. A 5mm brim is sufficient for 220mm tall pieces if you print slowly, otherwise increase the brim to at least 10mm. I wasn't able to print 220mm tall with the default MK4IS speeds.

Print T-Nuts with supports on the build plate.

Use the 2222 rails if you expect strength, you may tighten the T-Nuts as much as needed, they won't bend. The 20mm ones bend under tension.

I use 2222 rails with 3030 T-Nuts with M4 screws and nuts and they don't break when tightened.