I think I have enough loading manuals. I will just spend money and buy a pound of the powder and testerout. It really all started while I was trying to find a powder to use that's slower than H1000 but slower Than Retumbo. And I started to notice several powders on several different lists bouncing all over the place.
OOPS. I meant to say slower than h1000 but faster than retumbo.
I had a similar situation and tried the MagPro 215 Berger on my .300 WSM. While I got pretty good group and velocity, RL-17 gave me another 50 FPS with the same accuracy.
It really depends on what bullet and chambering you're loading for. Like others have noted, bullet manufacturer's like Berger, Hornady, etc ..., have conducted their own tests with various powders for recommendations.
RL26 is fairly new and hasn't made it to powder burn chart yet (at least not that I've seen) but Hornady for instance tested them on their 220 ELD-X in .300 WM chambering ...