I like to use one size bigger engine than you would expect for two reasons. one, to cempensate for the extra drag of a bipe and two, most bipes are built for aerobatics where the extra power helps. Flat top wing and a bit of dihedral in the bottom wing makes for neutral stability.
Ben. Still trying to get my pictures up but got as far as [ save to] and don't know where to go from there. To old to go to computer school!!