Hi Marco, do you have copies of the 1/96 scale Lambert plans? If so, if you look at the cross sections (59) it shows the column,it does look conical in my build but this is just an optical illusion. the perforated flanges adding to the effect. As for the space, there is in reality enough space for the crew to pass either side. I must admit it does not look pleasing to the eye, almost a desing afterthough. BTW if you need the set of the plans personal message me an address and I will post mine over (bit scruffy!)
Cheers JJ..