Thanks.
For the H2 example the sign actually matters for my construction of a wavefunction:
t = 0.1153404926
|CC> = exp(t * a_0 a_1 a_2^dagger a_3^dagger) | 0 0 1 1>
= 1 * | 0 0 1 1 > + t * a_0 a_1 a_2^dagger a_3^dagger | 0 0 1 1>
= 1 * | 0 0 1 1 > + t * | 1 1 0 0 >
The sign of t does influence a relative phase in this superposition and it changes the energy.
Maybe I cannot construct a wavefunction from these cc_amplitudes at all… I will read about the details of coupled cluster and see if I am missing some important points.