As Cracraft (1971) indicated, femoral position is not
always restricted to the parasagittal plane in birds, and thus there does
not seem to be impedement for gliding.
It is damn near restricted to the parasagittal plane _in *Microraptor*
itself_. Download the 2002 paper on *Microraptor* (Hwang et al., American
Museum Bulletin) and have a good, long look at the figure that shows the hip
region.