Thanks for the info Tom. I was actually considering using the V3 DL1 fixture for this architectural application. It is a straight down light, no knuckle. The client has since decided to postpone the project.
In the future, if you are looking for a completely water proof (IP68 no less) downlight for tree mounted applications, I would encourage you to check out the new Hyperion fixture from Illumicare. http://www.illumicaregroup.com/2011/11/hyperion/
It comes with a 30' long, factory installed / sealed, SJOW 16/2, lead wire which generally eliminates the need to make messy and unsightly connections in the tree. This is a category killer in my opinion.