Sorry, I didn't make myself clear. When I fly to KI, I cross at the narrowest point of Backstairs Passage: from vicinity Blowhole Beach to Cuttlefish Bay, about 8.5 miles. I assume 10:1 in the jab @ 65 KIAS, so over 6000' gives something of a safety margin. For the R22 (which of course I know nothing about), that crossing, at 6000' gives v little safety margin. Above that, a bit more.