ORIGINAL: AA5BY
My freeflight guru friend is suspicious that without any dihedral, the pitch control needs will be more demanding than afforded by such a config. Another config would be to put the elevons on the tail where no doubt pitch control would be adequate, but would roll authority be adequate... again he thinks unlikely to wit I tend to agree on not enough surface and not enough lever arm with them inboard.
Can you simply increase the dihedral and use rudder to bank?
If I remember correctly, those foam planes have a sweep back wing, which is equivalent to the conventional dihedral and conversions to RC have been successfully done without adding ailerons.
Check this search out:
http://search.rcuniverse.com/search....hwhere=subject