I needed a robust, lightweight stand for a RG65 r/c sailboat. It should be made from 15x15mm² Aluminium profiles as available in the hardware stores. Unfortunately, the necessary accessories are only partially available for 15x15mm² profiles. You will get everything for 20x20mm², but this is too heavy for a RG65. So I designed all the connectors, feet and end caps for 3D printing.
Most parts can be made from TPU which is perfect for feet and endcaps. It can be used also for 90deg connectors, but you should think about securing it by a small self-tapping screw. Otherwise the connectors might slip out of the tubes when carrying the model.
TPU is not recommended for the T-type connectors. TPU will not stand the permanent load by the boat and will deform. I made good experiences with PETG, but here it is mandatory to secure the connectors with a small screw.

Bill of materials:
4 feet 30 deg (TPU)
2 endcaps (TPU)
4 90deg connectors (TPU)
2 T-connectors (PETG)
2 side parts long Al square tube 15x15 380mm
2 side parts short Al square tube 15x15 340mm
1 top part (inner) Al square tube 15x15 279mm
1 top part (outer) Al square tube 15x15 310mm
1 stiffening long Al flat strip 40x4 340mm
1 stiffenig short Al flat strip 40x4 309mm
2 extensions Al square tube 15x15 150mm
2 supports Al square tube 15x15 150mm
2 screws cylinder head M4x40
6 washers M4
2 self-locking nuts M4
self-tapping screw for securing as needed
pipe insulation as needed
8 blind rivets Al 3,2mm
25mm belt webbing 40cm

Anet

A6

No

No

0.2mm

30%