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I'm not sure how to incorporate this, but including sleep hours/quality into the TSS calculation would give a more accurate assessment of fatigue level and help guide training choices.
I think what you are looking for is a way to incorporate other factors in to the TSB calc, but then it would not be Training Stress Balance anymore. HRV is another metric that you may find useful as well. We plan to add HRV as a metric in the future. Currently you can plot sleep metrics on the PMC in our mobile apps. This blog post briefly touches on that:
http://home.trainingpeaks.com/blog/article/new-ios-update-adds-charts