No it's not that hard with S. Sanchezi. You can check the serrae and compare it to that of S Rhombeus and be accurate (along with other visible identifying traits). See OPEFE for more details and identification keys of Sanchezi.
http://www.angelfire.com/biz/piranha038/images/Serrae_SsanOPEFE_1.jpg
http://www.angelfire.com/biz/piranha038/images/Serrae_SsanOPEFE_1.jpg


