So my first try at a custom strap didn't work (GPU crashed almost immediately when mining ETH).
custom 1900: 1500RAS, 1625CAS, MISC2, & ARB
777000000000000022CC1C00AD515A3ED0570F15B98CA50A004AE7001C0714207A8900A00300000 01B11353F922A3217
A straight copy of the 1625 strap to 2000 works fine, while the 1500 strap gave errors even at 1900. I tried taking the 1900 strap, RAS from the 1500, and CAS, MISC2 & ARB2 from the 1625 strap and using it for the 2000 strap.
Most of the time those type of adjustments will crash or yield no benefit. The timings that are affected by a change must be changed as well to compensate.
Secondly, tRAS has little affect on anything and is mostly changed to compensate for changes in other timings