Reporting back:
I like the garolite so much that I didn’t feel like waiting longer for the Lightyear to deliver, so I adhered my garolite to the least expensive Bambu Lab PEI sheet chinese knockoff I could find on amazon.
The good news: 10"x10" is pretty close to a perfect fit
The not so great news is that the 468MP seemed marginally more attracted to its own backer than it was to the PEI. In a more perfect world I would have applied it to naked spring steel instead. Nonetheless, it seems to have no problem gripping the garolite, and now that it’s on, I don’t think it will be going anywhere.
Worthy of note: From the X1C control panel you can disable the checking of the build plate. I did, and now I don’t get any annoying errors about it complaining the expected build plate isn’t there, especially since the knock-off build plate didn’t have any of the 2d markers on it. I suppose I could have copied the 2d marker from a real bambu labs build plate, but this obviates the need for that.
I just now completed my first print with the new configuration, and no problems to report.