Here's the response I received after emailing VihtaVuori about achieving 1450 fps in a 4" revolver with 125 gn hollow points. Although somewhat disappointing, I appreciated them getting back to me with this info because their website says not to ask for load data that isn't already available on their website:

"Thank you for contacting us at Capstone PG. We did some preliminary testing with the 4" length barrel and found that regardless of using N110, N105, or N350 with any of the available 125gr JHP bullets that we available to us, those being the Sierra 125gr JHC - 125gr Hornady XTP/HP - and 125gr Speer GD/JHP, there simply is no way to safely attaining 1,450 fps from this barrel length and to stay within the SAAMI Industry Pressure Standard that we must abide by in the interest of shooter safety. About the best that can be expected, depending the individual 4" barrel, is around 1,360 fps average. The shorter barrel combined with the barrel/cylinder gap does take its toll on what even the .357 Magnum will actually give us in real world performance. Please do not hesitate to get back with any of us with the Capstone Tech. Team if we can be of future assistance."

Thanks RDub for the follow-up pix and info. The N110 grains are definitely longer than those of the other VV powder I used. I think I'm leaning towards 300-MP now based on this latest info from VV and your data from earlier. AA #9 was also recommended to me on another forum as being somewhat lower flash so I might give that a try. What ever I end up using I will be sure to post my results here - probably around July if all goes as planned.