Gauge coupling and String Landscape?

[Benjamin]

Hi group,

There's this paper here, which tries to reproduce the precision
prediction of the weinberg angle and the gauge coupling in the
Supersymmetric standard Model

> http://arxiv.org/abs/hep-ph/0102306
> Journal-ref: Nucl.Phys. B606 (2001) 101

The authors claim that a heterotic string model would require extra
dimensions of a maximum radius with 10^(-14)fm-

Is this not a very strong constraint on the string theory landscape and
possible vacua?
That is, could this not be used to make some predictions from string
theory (at least if LHC finds the MSSM?)

Thanks,
Benjamin