Yes you can make the fork what ever shape you desire and with what ever materials but you do have to remember that for it to be solid and not ring like a tuning fork it needs to be made correctly.
The fork part is made from 19mm ply and in fact is basically 2 single pieces with the sides filled in .
All pieces are of triangular shape to maximise stiffness.
The whole lot is then fiber glassed coated and that is not that hard to do , a bit like paper mache`.
The fibre glass really makes it very stiff.
For a 12" only the whole lot could be scaled down to using 12mm ply and about 2/3 the overall size.
I can pick the fork up by my self so it is not a heavy way of going about it.
making it from steel is going to make it a heavy job to do ones self.
The inside is hollow but will be filled with expanding foam to stop the sound box resonance .
You could use steel or aluminum but that is going to increase costs.
The fork is made from only 2 pieces of 19 x2400x1200 ply plus about $ 120 of resin and fiber glass chopped mat.
I have gone about it as basically as possible and as cheap without compromising stability and only have basic tooling like routers ,circular saw, drill and hand tools .
I had to buy some of theses but factored that into the cost advantage over a commercial mount.
The whole thing is not going to cost that much more than a SSEQ6 and i know for a fact that an EQ6 won't handle my scope.
The steel wedge and shafts are away at the moment getting the motors fitted and drive and support rollers made.
At the moment i am in the process of redesigning my secondary cage so it rotates and allows viewing from all angles depending on scope orientation . Again only a router is required and is made from ply rings and aluminum sheet plus a bit of resin splashed here and there.
Any one want a heap of saw dust , routers are great for creating it and I got heaps
Mark