I just received my X1C earlier this week and out of curiosity did some bed flatness measurements today. I thought some of you might be interested in the results. I used this $25 indicator:
Amazon
mounted with this:
mount
I made 25 measurements with 50mm spacing so I covered 200mm x 200mm. I measured twice: once with cold bed and once with heated bed, both times without a plate.
At the moment, the cold plate has significant drops at the rear corners but it’s good elsewhere. When heated, it levels up pretty good.
I’ve been printing functional parts for almost 2 years almost exclusively with ABS so I’m not worried about the cold bed measurements at this time. If I ever suspect warping in the future, I’ll have these numbers as a reference.