Speed Up uniaxial Compression Test In Abaqus Explicit

Hi,

I am trying to run a uniaxial compression test using Abaqus Explicit, the simulation is using a cuboid specimen ( 2mm x 2mm x 4mm ) and the deformation is homogeneous, as I am using dynamic solver to analyze a static problem, the stable time increment is very very small, about 1 x 10^(-8). It would take at least 2-3 days just to finish the computation of an simple uniaxial compression test (with 25 seconds time step). This is really too long for me as I need to run at least 10 different uniaxial compression simulation with different strain rate. I am thinking since my specimen is cuboid and it's deformation is homogeneous, can I use 2D simulation like plane stress or plane strain simulation to proceed the analysis instead of 3D simulation, is it theoretical reasonable? If not can anyone suggest me on how to speed up the simulation? Like choosing certain mesh option and so on. 

PS: I have to use Abaqus Explicit because the next step is the implementation of a VUMAT 

Thanks and regards