Not sure if this is relevant but there's a section in RDH4 that explains an advantage that might be had on shortwave by having the oscillator frequency on the low side of the signal frequency when the oscillator injection is to the inner grid (g1) of the mixer.
RDH4, book page 991 (Section 25.2 (ii) B :
http://www.tubebooks.org/books/rdh4.pdf
Lawrence.