Curently I use 3.4g (grains) of Vectan AS behind a 158g lead bullet in my 357 Marlin but with the price increases on AS I've just looked at replacing it with Maxam CSB5 which as you say is quite a cheap powder.
Below are the results of my chrono testing:
3.4g AS gives 875fps
3.0g CSB5 748fps
3.2g 760fps
3.4g 838fps
3.6g 886fps
So 3.5/3.6g looks about right for me and confirms AS and CSB5 are not that different.
It is denser than AS though. My powder measure is set to drop 3.4g of AS and without altering it it drops 4.2g CSB5. For comparison it drops 4.4g of Viht 320.
The Maxam loads above worked OK in my Marlin but you'll need to check them out in your own gun to make sure they're OK for you.
I believe CSB5 is also OK in downloaded 44mag but have no expereince of this.