Nice detective work. :2thumbs: You have to love Google Earth. :nod:
You are free to post whatever you wish and ask questions as these canyons belong to all of us. If folks choose to help you or not in your quest that is their prerogative.
And when I hear the words pioneer used in regards to Lake Powell canyons I have to chuckle. Before the dam was built every inch of the shoreline had to be surveyed. The surveys were done from both river and rim. And those survey crews followed the miners and Anasazi that came before them.
You might find this useful when researching Lake Powell, it contains some good stuff.
http://silgro.com/LakePowell-hikes.htm#DougsSoundCave
It's from a hiker, but adventurous hikers know where the slots that stopped them are located and normally have good intel. :nod: