until 2010 when they raised the fairing up an inch, you had to use the roadglide specific lowers, for just the reasons you said. the batwing fairings have the adjustable vent, while the roadglide specific do not. a lot of folks have added their own vent in the lower. while not adjustable, it does allow for some airflow.
The Classic Motorcycle Vents are adjustable for airflow. With them fully open you do get a lot of airflow. They have tabs in them to keep the doors in the position you set them. With the glove boxes installed, you can't get to the doors while riding. That is the only downside. They fit both the older EG style non-vented lowers and RG style non-vented lowers. I'm not the only one with them. In fact, I found out about them on here.
2005 FLTRI Black Cherry, 95" Big Bore, Thundermax w/Auto Tune, V&H Dresser Duals w/Klock Werks SS, Andrews 26 Cams, SE Stage 1 intake, SE OD/6 Speed, Wards FCS cooling fans, Krome Werks Stretch Heritage +2 bars, Progressive Monotubes, 444's, & Touring Link, Michelin Commander II's, 14.5" Madstad, Lowers with Classic Motorcycle Vents, detachable King Tour Pack, Daymakers