Now admittedly, my RT is a 2013 Ltd with the 998cc motor, but I think this issue is related to the RT Shape rather than anything motor size related!
Anyhow, We used to have the same problem when my Missus rode pillion on my RT, especially that 'wet back from wet roads' thing!! She'd get soaked from water hitting the back of her helmet/jacket & running down her back, plus she'd often complain of the strong fuel/exhaust smell too! Since my RT Ltd came with the 2 largeish vents in the lower section of the screen, I didn't go down the path of adding further vents in that. Instead, I played with a few ideas aimed at cleaning up the airflow behind the panniers & trunk thru adding fairings or 'wings' on the tupperware instead, but, none worked well until I hit upon fitting an extendable trunk lid rack. Fitted that & problem solved! It works very well with the 1/2 cover on the rack, & I added a flat filler of 1/8th inch ply when the rack isn't in use; result is that all the problems associated with that 'air turbulence' thing, the helmet lifting off, the buffeting, the exhaust smell, and the wet back issues et al are all gone!! :2thumbs:
So I reckon the issues many experience are mainly due to the std RT &/or larger screens creating a fairly big low pressure area behind them & where the rider/passenger sit, so that the low pressure area behind the panniers & trunk merges with the screen low pressure area & together the problems are worse, basically sucking all the turbulence & road spray, exhaust smell etc into what's meant to be the rider/passenger 'still air' zone!! Adding vents to the screen (if you don't have one already) might help, or as we've found, by simply by fitting a 'whale-tail' type trunk lid carrier or airfoil on the top of the trunk, you can iron out the air flow over & around the bike, moving the lowest air pressure into the area behind the trunk & so helping to keep the pillion in the largely 'still air' bubble formed by the screen that the rider usually enjoys! I'll try to put up a pic....
