Hi JP

I forgot about this recent article I read but you may find this useful for your patient. It examines the reliability of a measure for kyphosis using a two readings from a bubble inclinometer. if you don't have a bubble inclinometer it is a very useful goniometry device to purchase and there are multiple protocols available for various measures of posture and ROM of different body segments. Personally I prefer it to a standard arm goniometer.
The background to the article also covers some of the health issues that people with kyphosis may experience so that and the reference list may be quite informative

BioMed Central | Full text | Clinical measurement of the thoracic kyphosis. A study of the intra-rater reliability in subjects with and without shoulder pain