low occupancy of the DDR in HAN Pilot platform with opencl

I have a simple vectorized code with just 4 reads and 4 writes in the DDR with a clock frequency of 360 MHZ and i only achieve 10.6% occupancy for the read with a bandwidth of 612MB/s and the same for the writes. When i lower the frequency (for example 200 MHZ) and increase vectorization for example 8 or 16 i get at most an occupancy of 25% and a bandwdith of 1600 MB/s for both reads and writes respectively.

The fpga that i use is the han pilot platform. Is there a way that i can increase the occupancy? I attach the .cl and host file.