Add 10% to .38 special case load data and you’ll achieve very similar results in a .357mag case.
Personally, I use 4.5 grn Bullseye under 93grn Meister LRN’s, and 5.0grn HP-38/W231 under a 125grn plated bullet (still chewing up inventory of Rainier bullets, but also have used this load under jacketed Remington SJSP’s). Built for use in J frame/SP101 and ultralight alloy revolvers, these loads are a remarkable pleasure in a vintage 7.5” Redhawk.
ETA: I reread and caught your question about W231 and existing load data. If you examine the pressures of that .357mag data, you’ll see it’s exceeding .38spcl levels - in this case, the exclusion of data is due to a publishers concision, not due to any safety factor. 3.8grn minimum in a 38spcl case scales to 4.2grn in a 357mag case - THAT is your minimum in the .357mag case and your max is the published 6.9grn. 5.0 will be safe, under the appropriate bullet weight. As mentioned - 5.0 W231/HP-38 under a 125 is one of my pet loads.