  We explore the phenomenological predictions of a supersymmetric standard
model, with a large extra dimension and unifying gauge couplings. The modified
five dimensional renormalisation group equations make it possible to obtain
light, maximally mixed stops, with a low scale of supersymmetry breaking and a
low unification scale. This allows the fine-tuning to be lowered right down to
the barrier coming directly from experimental lower limits on the stop masses.
We also show that attempts at modifying the SUSY breaking pattern to obtain
more natural soft terms at the high scale do not give the expected fine-tuning
relaxation, and only RGE effects turn out to be effective in generating a lower
fine-tuning.
