Nice to know it's been done before!
Thank you all for the information. It would be simpler, more certain, and maybe faster to drive from one trailhead to the other, but not as interesting. I'm planning on this as an overnight trip anyway, so I'm not too worried about it taking a while.
I am glad to hear that the woods in the notch are open, or at least that some of it is. Sounds like if I follow iceNsnow's advice and leave the Big Slide trail at or below the jct with the Slide Brook trail, I'll avoid the cliffs and steeps that Guinness and TCD warn about.
I also learned that an RWMS group did this route in January 1997, and made pretty good time. I'm going to contact members of that group for more info on routefinding.
Watch this site for trail condition and/or trip report post after w/e of January 13-14.
Thanks again, all.