My son has a park flyer - a pretty extreme one at that. His eFlite Mini UltraStick is definitely an outdoor plane and uses a DX-7 with the AR-6100 receiver. I've heard some folks get an effective range of 600-700 yards with this receiver but I would have opted for the 2-part AR-6200 or AR-7000 full range receivers for migrating from 72 MHtz gear.

As far as the servos not fitting correctly, some servos (notably Futaba) have a key on the connector that you can cut or file off to fit the Spectrum receivers. Just remember which color wire is what pin.