I do think that taking the last three contiguous panels in a level as a block is bad colab-form. (I've done it myself, and will almost certainly do it again, but still think it's bad form.) Also, I think the

"simply flip the square you're butting up against, and chip away/draw on top of it"

So, all in all, a somewhat disappointing finish to 3266, but I've seen (and done) much, much worse in the history of the cosm.