The U-Can-Do is a pretty awesome 3D'r, but it is a SLOW flying plane, thanks to those large control surfaces.

At high speeds flutter is a big issue, so it is recommended to prop this plane down for a lot of torque with lower pitches.

My Giant UCD 3D uses an 18x6 APC prop, and I wish I could go to an 18x4W, but no such animal.