Use of an IGH with vertical dropouts also normally requires use of a chain tensioner too, the reason I do not personally favor choosing such a frame for gear hub installation. The exception is a frame such as the Civia Hyland which has bolt on semi vertical dropouts but tensions the chain via horizontal dropout adjustment. Another option for chain tensioning with vertical dropouts is an eccentric bottom bracket as is done by Thorn cycles in England. I believe the frame needs to be specifically designed to take advantage of that method however.

The Civia offers 3 interchangeable bolt on dropout designs; one for the Rohloff IGH, one for the Shimano Alfine IGH and one for rear derailleur mounting. SRAM now lists anti rotation washers to fit the Rohloff standard dropout angle too for use with the iM9.