Which shock mount is best suited for the Audio Technica AT 4047?
Both the USM and USM-L would work perfectly fine in the vertical position.
However, if you have heavier microphones that you would also like to use in the shockmount. I'd opt for the InVision USM:
Description: InVision USM
Order Code: 044901
Web link: www.rycote.com/products/044901
InVision USM and USM-L from Rycote on Vimeo.