Hi kwb737,
Rhumba made clear on several occasions that everything he developed with corrected elevation data would conflict with any correction made previously to the stock sceneries.
This includes his early world coastline flattens like this one you found at Simviation. "Rhumbaflappy" is Richard Ludowise' web pseudonim.
He also advised against using his old water flattens on top of his newer mesh, as it would create even worse mesh conflicts.
It's the same old dilemma with PTO ever since Rhumba's new mesh and flattens were released. They are a very accurate work, but they create more problems in the PTO, with all of its thousands of small islands and coastlines, than the rest of the world.
After a while, I had to revert back for my PTO install to the stock mesh, nicely corrected with early Rhumba's water flattens. Our good Rami suggests to do the same, when installing his great PTO campaign packs.
Cheers!
KH