What I heard about that phil type was that it could be tapped side to side for centering, but shouldn't slip. I was also interested in the vo bb, and cutting out the frame tubes in the way, but still wasn't sure how or if it would fit that bb shell. The vo site says it won't work on itallian bbs. Not sure exactly how to measure the viscount shell, as there is that step up in inside diameter for the bearings.
Also, just checked that old broken spindle, and it broke right along the end of the tapers, so maybe the c clip grooves weren't the main problem.