I've never seen the powder brand here in South Texas, but I might be able to help you a bit with it. VihtaVouri 32C is the renamed Tin Star. It is similar to Hodgdon's Trail Boss, which are low pressure and velocity cowboy action powders. They are bulky powders to fill the case and burn clean, a great alternative to black powder. I wouldn't overthink either of these powders. In fact, Hodgdon has a PDF sheet (attached) on how to determine TB loads if there is none available.
You have probably seen the VV32C data from their website.
VV32C 44 Mag.jpg
I would take the bullet that I'm going to use and follow Hodgdon's instructions about marking, filling to the mark, measuring, and then the math to see where the numbers sit against the VV data.
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