"do not fill above the upper mark; you could damage the engine" so I reasoned in the middle was the ideal spot.
Yes, but remember the level is likely to
decrease as you use the vehicle. A bit may leak or get burned off in the normal operation process.
For most of us, an oil level near the top of the range continues to remain well into the "acceptable" range thru the usefull life of the oil and won't likely require topping off before the next oil change.
The level is not likely to increase, except if something goes wrong , like a fuel injector leaks and floods the cylinder w/ extra gas, conbustion stops happening(no spark,etc) and adds fuel, or a head gasket goes and adds coolant to the oil.
In any of those cases you've got bigger issues than "oil level", and even in a best case scenerio, you'll want to change the oil after fixing the problem.
Keeping the oil near the upper range is a good idea.
