What rules does the Catholic Church have for venerating crosses/crucifixes on Good Friday? Each year on the Good Friday service at my parish we venerate the cross, but I really wish it were a crucifix, and I've wondered why we don't have one for that purpose.  I've been trying to find one to just drop off at the church with a note saying "this is better, keep it", but before I do, I would like to know if the  Catholic Church has any restrictions as to what kind of a cross can be venerated during the Good Friday service?  

Does the cross have to be a certain size, of a certain material, or are we even allowed to venerate a cross sans-Corpus?
The rubrics for the pre-1955 Missale Romanum (PDF p. 326) seem to assume there is a front and back side of the cross, which could only be possible were there a corpus on it:


  Completis Orationibus, Sacerdos…accipit a Diacono Crucem jam in Altari præparatam: quam, versa facie ad populum… etc.
  
  The orations having been completed, the Priest…takes the Cross,
  already prepared at the altar, from the Deacon: which, [the cross] turned
  toward the people… etc.


It can also be inferred that the cross shouldn't be so big that it can't rest on the altar.