Hey Scott, which Viberg Chukka do you have in mind? It depends on the last the Viberg is built on. I tried the 110 last in a size 9, which is my TTS US size and the Viberg 110 last was a little longer than a US 9 but was wider, maybe a E or EE in width. I hope this helps, most of the guys here are much more versed in Viberg but if you can point out which last you are looking at they may be able to help.
Viberg's are solid boots and I hope you find something that works
All the best
Thanks. It's the 110 last. Maybe I should go down half a size...