The original reason for this proposal was the desire to produce an apartment building with the proportions of a smokestack but it turned into another exercise in using small and few changes to generate apartments of various sizes within a rigid system. This for me is the attraction of superslender planning. 

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As with the various iterations of the Universal Apartment, apartments of various sizes are configured by utilizing an internal stairwell shared by more than one apartment. This configuration is essentially one half of the Universal Apartment III that has been turned in on itself. It does not have independent access to all rooms but is nevertheless another validation of the advantages of internal stairwells with multiple access.  

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Sellable area (a.k.a. floor plan efficiency) is 81.1% good, and because it is exponentially linked to the radius, can be increased to the magical 85% by increasing the radius 60 cm from 7.54 m to 8.14 m.