Not sure why you need finer grain from 5x7, but I would suggest trying a finer film. TMX, Acros and PL-25 are all available at least in 4x5 and are exceedingly fine-grained. If you want an even smoother look at the cost of resolution, use a more-concentrated solvent developer, e.g. Xtol or D76 stock, i.e. no dilution. Or go for TMY2 if you need speed; it's finer than most traditional ISO-100 emulsions like FP4 and Fomapan.