Mark, since I once turn rather than twice turn, access to the bottom of the bowl is not necessary for me. I did ask a long time ago about those who twice turn, wanting to know if they did their finish turns when the bowl was reversed for truing up the tenon. Maybe half did. I have trued up bowls some times when they are reversed. I start with a BOB tool for the first inch or three, then switch to a 40/40 as I get closer to the rim. Since I use a recess, I can access the bottom near the base easily. With a tenon, I can see where it would this would not be as easy.
As for the cone adding to vibration issues, if you don't use the tailstock, which I don't, then it is an issue. If you use the tailstock, which many do, then it is not an issue. The farther a piece cantilevers out off the headstock, the more vibration there will be. This is physics. Take a look at any hollow form turner, and they will all have steadys on their longer pieces.
I have had a Laguna 16 HD bandsaw for a number of years, and it cuts 16 inches high. When it arrived, it was damaged. They had bolted it to a cheap pallet with tiny bolts, and 3 of them had come loose. The shippers had tied it to the inside of the truck by a strap around the upper blade guide and bent it considerably out of shape. When I complained, they asked if I had any pictures. There were few cell phones at the time, so I said no. They pretty much said tough luck. I would expect that I was not the only one to have had this problem, and I doubt that they ship without the piece being in a crate any more, which is the way they should have done. I won't be buying any more of their tools. I wish Robust would build a big bandsaw....
robo hippy