RattyMouse,
It's my understanding that the first couple of seconds as the film is being ejected is critical with regard to light exposure. Folks use all kinds of "tricks" to shield the film such as ejecting into a black plastic bag, ejecting into the empty cardboard film box, use of the normally trashed darkslide as a make-shift frog tongue, an actual frog tongue, etc. Even turning the film upside down and placing against the bottom of your SX-70 might be too late depending on external light levels. FWIW, anyway.
Yeah, I've shot quite a bit of B&W 2.0 film as well as the prior version and IMO it's tricky to deal with and cumbersome to learn. For example, I've read (and believe) that the actual film speed of the B&W 2.0 film is somewhere around ISO 300. Given that the SX-70 is expecting ISO 160 film it's pretty easy to see why the IP film is over-exposed with the L/D wheel set at the center mark; and why we have to turn the wheel all the way to dark to get even close to a correct exposure. I've taken to using colored filters or ND filters over the lens to reduce the speed of the film which works pretty well. The 2.0 film seems to have more contrast than the prior version, but that's another story...
Lately, I'm finding more fun and enjoyment shooting the color film. I'm not much of a color photographer--been shooting B&W for 40+ years--but the soft, muted, sometimes washed out color of their color film seems to appeal to me; and I don't know why!

If you haven't already, you might want to play with a couple packs of the color film just to see how that goes for you. Order from IP to ensure you get the latest version; there is actual a newer emulsion available now.
Good luck!