I have been thinking about risers for handlebars and the question of how much tolerance is in the cables. Over the years I have read on numerous forums about people that would like risers but are unsure how high they could possibly go.
For risers all you would need to do is undo the bolts from underneath the triple tree that go up in to the stock risers and build up a mock riser out of anything you have lying around such as washers or nuts, then bolt the original risers and bars back on & turn your handle bars to full lock. As long as your cables are not being stretched then what ever the maximum length it is that you have gone to is the total riser extention height that you can go to. You may need to use a longer bolt for this experiment as I have noticed a lot of risers come with extended bolts.
Simple but affective.