I haven’t looked at the 1040 specs or review but I’m interested in what the 540/840 may be. I’m currently awaiting the arrival of my 5th replacement unit that started as a 530 but is now an 830. I’ve had 3 530’s and an 830 all of which end up with malfunctioning barometric altimeters. I’d say they’ve used random number generators instead but all except the 830 worked for a little while but then ended up either way over or way under estimating ascent/descent data. So my wish for the new 840 is a functional altimeter.