I didn't say we should expect MINIMUM 80 km/h. I'm saying that with good design 80 km/h could be sufficient. But so could 60, or 50.
And if you say that under that speed aerodynamic stability can't be reached then wouldn't there simply be insufficient external forces to make LOHAN start tumbling before she reaches that speed in the first place? With the rocket aligned to thrust through the CG there would simply be no forces big enough acting on her to cause a tumble before she reaches sufficient speed for positive aerodynamic control to kick into effect.
Even at 1/3 the acceleration, thats still close to 27g. An airframe designed for high speed flight does not necessarily be able handle 10g longtitudinal. Infact, most airplane designs are remarkable fragile in that direction. Because they never have to experience an acceleration that big in that direction and the entire mass-moment inertia of the wing has to be taken up over the small distance between the mounting points (Which would be even smaller than the wings root chord and not that much compared to the wing length. Aerodynamic drag in the longitudinal direction is by far not as big as the forces created by acceleration forces in that direction. I'm still very sceptical about trying to raise the initial launch acceleration.
Once again, the design boffins will have to give the final word, they have the exact design (and probably some shiny Finite Element Analysis software) and can calculate the maximum stresses and related accelerations.