Hello Nuno
I fitted a steel tabernacle on my 7,20 meter boat . I bought a heavy square tube from which I've cut out the front side until deck level . I believe it has a wall thickness of 4 or 5 mm . As pivoting point ,I just drilled a hole through the mast . (Shouldn't be a problem for me , because I made my mast from 2 aluminium tubes and I put the 3 meter offcut at the bottom of the mast which produces a thickness of 8 mm right there )
On the topside and on frontside bottom of the tabernacle , I welded flanges where I bolt on the frontside a shield and a corner profile and on the backside only a corner profile to keep the mast up . The shield I put there is to support de diagonal strength
Make sure that the plate I welded at deck level slopes down to prevent that water remains in the tabernacle .
All in all not the most beautiful tabernacle since I'm a amateur welder , but it's functional for my estuary cruising .