Just for general information...
It can be done and has been done. take a look at
http://gossamer-threads.com (the software that is used here for the resources section among others). They converted a HUGE UBB. They closed the site for about a day but they made many changes... I have no idea how they did it but it seems to work very well (my username and password work and UBB was awful with the activity in their forums). Hopefully their experience may eventually help others...
