Also, if you are using "above start" make sure the transmitter has a good fix on satellites before starting the recording. If it has an inaccurate fix when you start, all the readings after that will be off because it thinks you started at a different altitude. It sounds like in your example in post #9 that it had an inaccurate reading of 300 feet higher altitude than actual when you hit start. That would put all readings after that 300 feet lower than they actually are.

I put it in "EXT" mode when I start running my dog. When I get a point I switch it to "HD" mode. It uses very little battery in "EXT" mode, and this gives it plenty of time to get a real good fix on satellites. When I get a point I switch it to "HD" mode. It switches real fast, and has a good accurate reading for the start of the flight.