You have to notch the back bone for the carb, and a there a mother f'er to do any on the machine carb adjustments, have to pull airbox back and snake out the carb to do anything.  the earlier ones are better if you run open filter. If you need a Airbox the Later and the earlier are way easier to do ride height and sock adjustments.
I will be doing a new hybrid with a later chassis here in the future just for the airbox reason.  If I don't just do a whole frame.