Hey, Look out, I got the ol sweet tater up to almost 3000 feet last winter. I had a headache for three days.There is a guy posts on here named T-Cart. He has about 19,000 hrs and is a retired crop duster. I am chuckling to see what he would put. "Well, I got up to 500' on my way to a field one time" or "Got a little high while spraying once and ended up at 15'"
FL210 in a C421,
10,500 in a Piper Clipper.
10,000 ft isn't the slightest more dangerous than 1,000ft, but don't tell me it doesn't feel that way in a rag wing airplane.