Valid ranges of tuning parameters for different setting of CR132, PHYs ...
It may be possible to improve the range of RD (CR105, CR110) using the 0x505 setting on board Rev H:
I would recommend changing PHY_RDLAT (DDRMC_CR126 bits [13:8]) = 0x9.
This should give the Read Burst one extra cycle to complete. This is important because using RDLAT_ADJ = 5 starts the Read timing for the pads one cycle earlier.