OK after a few re-reads of the manual and then the mysterious loss of my flight record to prove my point about a vertical fly away mentioned earlier I've done some re-thinking. It's called things not in the manual. First is setting imperial measurements has no change on setting values for failsafe height AND maximum height. Failsafe and Max height are ALWAYS IN METERS. So when I thought I was in feet watching my telemetry at the 300 foot level and executed a RTH she busted through my 400 foot ceiling cap which likely was set at 400 METERs.. In fact it was on its way to 1200 ft = 400 meters when at about 800 feet I cancelled the RTH. Thinking I had a flyaway on my hands and no choice I did another RTH she mercifully came home without going to 400 meters. Perhaps the power level overrode the climb and she just headed back.
Further testing at much lower altitudes proved that RTH will override your max ceiling setting. Other newbie tips is the home point will not be setable unless the props are spinning or you did an assisted take off...which is sort of scary since I'd like to hear the audible confirmation "The home point has been updated" before the aircraft is airborne. Still got that vision of the I1 taking off and slamming into the steel garage door YouTube video in my head.
Another issue I'm testing is at what distance from a home point will trigger a failsafe climb? Seemed in a few flights when less than 20 ft away, she didn't climb after a RTH command. Just scooted over, dropped gear and landed. Perhaps a parallax viewing illusion. Will do more flights to confirm. Testing was done with 1.3.0 firmware installed. Seems now bird won't spin up at all when under 10% no matter how fast I cancel the auto land command. Wanted that feature to the pack calibration after 10 battery cycles. Otherwise gotta wait hour(s) for battery to drain to auto shut off level.