Hi I'm over 6'4 and love the xtx, the wife has jumped on the back a few times for trips out and it's been fine,
I don't think any bike is really great 2 up, unless it's a pan european or a goldwing or of that ilk

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K+N filter, snorkel removed, homemade kev mod (with his blessing), co raised,
Pipeworx cans, r1 led back light, under tray removed, small indicators, handguards, cnc short levers,