I only got through to 5.1 but I can at least inform you on that. If you can teleport to Vzahl, it takes I believe about 20 minutes to get to the BC. If not, I would say more like 45. They are just rough estimates though. I would set aside an hour or more to expect 5.1 done. Also a good idea to get some high level assistance or carry a goodly supply of prisms and powder. A map is pretty helpful too. Its been a while but I would say an hour tops is about right. But if you can teleport maybe 30 tops.
Faedryth