The simplest way to convert a low-wing monoplane to a bipe is simply to slap on an additional wing of the same dimensions. A friend did this with a Sig Four Star, and the result was a sweet flying, fully aerobatic bipe, powered by a sport .61. It is essential, however, to double the area of the tail feathers. The vertical tail area should be at least doubled, since bipes wings and cabane struts dirty up the air flowing over the tail. I recommend a vertical tail (fin and rudder) with total area of at least 15% of the combined wing area. I don't recommend clipping the wings at all.

Another friend clipped the wings quite a bit of Four Star bipe conversion, and his airplane was not a friendly flyer at all, even with a .91 up front. This was largely due to the effect of mutual wing interference, which lowers the effective aspect ratio. A biplane wing of aspect ratio 5 will have a monoplane equivalent aspect ratio of about 3.5, which means - a whopping increase in induced drag.