Gryphon
I can recommend enquiring at Kwalata Wilderness & PH Jaco Strauss in the Limpopo. I had very good hunting there last year. It is hilly to mountain country and I was hunting buffalo but I saw some damned good kudu. Several that were 54 to 58 and at least 2 that were 60+. They were not on my list having got a good one in 2010 with Jaco on a different concession.
Jaco is a great PH, straight as a dye and works hard to get what you are after.
Your mate will require a moderate level of fitness for Kwalata.

Cheers

Jon