Definitely going to be stronger and stiffer with more bracing round the back offset by the extra weight of the tubes.
I wouldn't bank on it being stiffer...the bottom bracket is where you need the most stiffness....so that is where you want the most support. Normally all the tubes converge there, giving the stiffness from the triangulation of the back end.
Having the BB in the centre of the tube will decrease stiffness.
The more open rear triangle will be far more flexible, as smaller and tighter triangles are stiffest.
I'd be very surprised if adding a second triangle by using the skinny mid stays would make that back end stiffer than a regular diamond frame.
The BB having no chainstays mounted either side behind it means it has nothing to stop the twisting forces that pedalling would impose on it.
I wouldn't bank on it being stiffer...the bottom bracket is where you need the most stiffness....so that is where you want the most support. Normally all the tubes converge there, giving the stiffness from the triangulation of the back end.
Having the BB in the centre of the tube will decrease stiffness.
The more open rear triangle will be far more flexible, as smaller and tighter triangles are stiffest.
I'd be very surprised if adding a second triangle by using the skinny mid stays would make that back end stiffer than a regular diamond frame.
The BB having no chainstays mounted either side behind it means it has nothing to stop the twisting forces that pedalling would impose on it.