How to model an interior spiral stair in Sketchup

Описание: plugins used:

s4u stair: https://sketchucation.com/pluginstore...
s4u slice: https://sketchucation.com/pluginstore...
1001bit pro: http://www.1001bit.com/pro/download.html
vertex tools 2: https://evilsoftwareempire.com/vertex...
shape bender: https://sketchucation.com/pluginstore...
curve maker: https://sketchucation.com/pluginstore...
soap skin bubble: https://extensions.sketchup.com/exten...