A little mechanical info on a carbide stalk:
I found an elastic beam calculator and I think I did the right thing to get the deflection of a single stalk.
First, the design: a 1/4" carbide rod thinned in to a rough elipse (cross section: 0) 1/8" wide. The calculator uses metric so to be conservative, I'll say 3mm.
An elipse will be much stiffer to bending to forces applied in the plane of the long axis so to get a worst case, you calculate for a 3mm round bar and halve the deflection because it's going to act like two 3mm bars bound together (cross section: 8). It will actually be better than that because 0 has a bit more section than 8.
Carbide has a Youngs Modulus of 550GPa, the moment for a 3mm bar is 3.9761e-12 m^4 and I put in a 200mm beam length with a .25N force.
The resulting deflection was 0.3048mm, divide by 2 to approximate an elipse and you get 0.1524mm or 0.006"
I think that is decent but I would still minimize the weight of the secondary, minimize the length of the stalk and consider widening the elipse based on how heavy it is.
If you put this in a Dobson with the stalk prependicular to the elevation axis, it gets better because the force of gravity will always be acting on the stiff axis of the elipse.
If you incorporate the sag of the secondary stalk in to a Serrurier truss design, you can cancel it out.
Any way, I think a single stalk is half way decent until your aperture and secondary get huge, for my 12" f8 project, it looks promising.