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The 1 piece 2-in-1's are going to be heavier than a tablet because of the keyboard and larger [probably] batteries. I use a stand though. It's going to be difficult, if not impossible, to find a relatively large screen device weighing less than the ipad pro. My 13.5 in is 3.1 lbs, HP's are about 2.9 lbs. Surface pro about 2 lbs. Ipad pro about 1 lb. The new Boox e-ink is about 1.3 lbs.  Using a weight limit as a primary concern, you will probably have to look at the 7-9 inch phones/readers/tablets and consider their ability to page/scroll and annotate, along being able to read the charts.