The entrance to Twin Dees definitely is a tight squeeze. The first couple of times I tried to get in there I didn't get it quite right and was denied because I was getting my tanks keyed in the final little restriction. After laughing at me, someone else on the surface told me to rotate at the 30' mark, and viola.
It continues on as small cave for about 1200', then pops out into the first big room. By small I mean small -- 3-4' vertical clearance for the first 600' (but perhaps 5-6' wide), then 3' wide for a bit with a lot of vertical relief, then back to 3-4' vertical clearance. Then you pop into the first big room "the beach", where the bottom drops down to over 200', the ceiling is probably around 90'-100'.
[video=vimeo;102633948]https://vimeo.com/102633948[/video]
