Good idea (other than a girlfriend who wears pink nail polish...).
In this case, the horse is out of the barn (and the old sleeve is in the dumpster). I do think I'll do the same thing (with a silver sharpie pen I use for things like this) on the new sleeve already in the tranny, and then push it in "with vigor" (and a pry bar this time). If the silver mark disappears, I'll know it's fully seated.
I think I'm the victim (hate to use that word though) of some semi-misleading info. From what I'd read, it's impossible to close the sleeve latch unless the sleeve is fully inserted. I believe that's not true. I also read (several places) procedures for installing the sleeve that just involve pushing it home with your fingers (and no mention of having to be able to puncture plywood with those fingers to qualify).
The good news is that I'll know for sure whether that's the problem soon... spent the morning running around... now it's time to get greasy (again). First job - scrubbing out my catch pans so I'll be able to re-use the fluid, or at least most of it (had a couple quarts of new fluid left and will put that in first when I button it all back up).