I have tried a lot of saddles and I find that I can't do any that have a strong arc or curve. It's too much of a "taint blaster". Unfortunately, I've found that almost all leather saddles have either too much arc, or are difficult to get into position. I have found a number of modern saddles that I like.
Specialized Power and Toupe saddles - 155mm width for me. These are flat and feel stable and comfortable. However, they do work best with padded bike shorts if the ride is long, and can start to get challenging after a couple hours without a padded chamois.
I also have a Selle SMP "Plus" model as well. This has worked great on my Riv; correct amount of padding, desireable shap, but OH IT'S UGLY!!!!
I revently picked up a Rivet Imogene saddle from this forum. It's a flat, pretty wide saddle. I THINK it's working, but I"m waiting for a longer setback seatpost before I decide for sure.
But holy hell, saddles are a litera and figurative pain in the ass until something comes along and you ride and stop thinking about it.
Cheers!
Ben