RE: sPPED PROP FOR sAITO 91?
APC lists 11-12,11-13, and 11-14 pattern props, so getting a bunch of pitch in 11" diameter doesn't seem to be a problem. In narrower 12" props, they list 12-11N, 12-12N, and 12-13N "narrow" pattern props. If the airframe is clean enough, one of the high pitch 11" props might be the ticket, but experimentation is definitely in order, as is watching your static rpm.
mIKE d.