I load that bullet at 1.240 OAL and use 3.5 or 3.6 Grs of WST or Competition. The recoil is light, it shoots very well, and gives around 700 to 750 FPS in 4 to 6 inch revolvers depending on the gun/barrel.
That should be a safe place to start with Unique, making sure all bullets exit the barrel, then work it up as needed. I would think in the neighborhood of 3.8 to 4.0 would do the trick. If you load it shorter, it would take less powder of course, but it is a long bullet and you start jamming the bottom of the bullet into the thick part of the case if you try to load them flush.
We don't have much to go on from load data using the Berrys 148 Gr HBWC. Alliant shows a Speer 158 Gr LSWC at 1.440 OAL giving 815 FPS using 4.7 Grs of Unique. This is a max, so 10% less would be our starting data. The Berrys is 10 Grs lighter, but loaded deeper.
This is what I base my educated (?) guess on. Be careful, good luck, use my guess for Unique (Or my other load above) at your own risk, and hopefully someone who has used Unique with this bullet will come along and share their experience.
Welcome to THR.