If you were first trying to determine your maximum travel by unscrewing the fork caps and just letting the forks slide down to the bottom then you will not get an accurate assessment of the actual travel. The fork has to be fully assembled, with springs, etc., and then you have to "pull" it down, much like you have with the straps. Usually this measurement will be as much as an inch less as one taken with the forks semi-disassembled. Few forks I am aware of these days use any sort of bottoming "cone" like the old damper rod forks, yet some actually have bottoming "bumpers", much like a shock, but looking at the parts diagram of the Super Ténéré fork it doesn't appear it's one of them. In fact, internally it looks like most upside-down sportbike forks around these days, and from my experience that means the springs run into coil-bind as the fork bottoms out.
BTW, using different springs, particularly if they are of different wire gauge thickness or are wound with more or less coils than stock, can significantly change when this coil-bind occurs. Again, the only way to find out is to fully assemble the fork and "pull" it down until it well and truly bottoms.
One thing, you can make it a lot easier on yourself to check for this point of coil-bind if you pull the forks, drain out the fork oil, then re-install the forks and check the travel. With oil in the forks there is less air-space above the oil and this acts as a spring, but a very progressive one, and as you get close to maximum travel it can get *VERY* stiff. So stff that some fork makers actually use this as their bottoming stop in sense, specifying fork oil height/air volumes that literally bring the fork close to hydraulic "lock" just prior to spring coil-bind.
But this can be your friend if you start to run into clearance problems, that is if you can live with the near full-stroke harshness... That is, if you are bottoming out and using the forks full travel to coil-bind and hitting your header pipes or skid plate with the 21" wheel, you can raise the fork oil height in the tube. This will effectively *stiffen* the spring rate throughout the fork travel, but will really spike it near full-stroke... If you want you can keep raising the fork oil level until there is literally no way the wheel can hit anything. Only problem is you may not be getting all the travel the fork has to offer and the ride will be much more harsh through the stroke of the forks.
Hope this helps.