I am 6'5" and I often sit on the passenger seat to stretch out my legs. Might not be an option if you have loaded this area with luggage... or a passenger. My second, well sometimes first, option is to just stand up. I have done my whole commute standing and it is a great way to stretch you legs. It is also a very cheap mod

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Yup, standing works best, shake ya bum a lil to get bloodflow in the legs going again. Also a fan of throwing it back on the passenger seat.
If it's really boring straight ish roads I also like to sit perpendicular (both legs on one side of the bike) or cross legged (put one leg on the saddle, under your bum). Do not recommend doing this in traffic though.
Gotta watch since Standing up is illegal in some US states and Countries, need to be seated, otherwise you might get fined, depends on LEO's mood
Amongst the fanfare of British Columbia Ministry of Justice’s April 30th, 2012 announcing new motorcycling laws requiring DOT, Snell M2005, Snell M2010 or ECE certified helmets are far reaching pen…
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In the Netherlands we have what's called the "anti fun law", or better known as "article 5" which cops can randomly hand out for everything they deem "dangerous". Standing, sitting, doing wheelies, burnouts, riding without hands all go under that category; most cops however don't care at all if you're not pulling a wheelie with 100kph past them.