Producers of the NBC series “Against the Grain” have put on what amounts to a final full-court press to “save” the Friday-night drama series, which has completed production on its initial eight episodes with no word regarding an extension.The Warner Bros. drama is fast becoming this year’s “I’ll Fly Away”– it’s perceived to be a quality show that simply hasn’t made a ripple in the Nielsens as part of NBC’s Friday-night lineup. Producers/co-creators Michael Pavone and Dave Alan Johnson, having already received endorsements for the show’s “family values” from conservative TV watchdog groups like the Media Research Center and the Rev. Donald E. Wildmon’s American Family Assn., have sent a six-page letter to network brass pleading for one more chance. The producers cite the shows qualified endorsement by Viewers for Quality Television, viewer response, positive reviews and assurances from more than 40 critics they’ve contacted3that the scribes will lobby for the show. Because of the small-town drama’s tone, they add, “(We’re) convinced NBC could score major PR points with the public, press and the network-bashers in Washington for picking up one of the lowest-rated shows on the network because you all believe in it and the positive family values which it represents.” “Grain” has averaged a slim 6.1 rating, 11 share in Nielsen this season for six airings. With the arrival of CBS’ “Diagnosis Murder,” the show has run fourth in its time period the past three weeks. The series will be bumped by specials for the remainder of sweeps and won’t return with its final two episodes until Dec. 17 — the second to air on Christmas Eve, a night of extremely low viewership. NBC hasn’t made a decision regarding the show but is reportedly considering Paramount’s action hour “Viper,” featuring a souped-up car, as a possible replacement beginning in January. Warner Bros. TV and the Lee Rich Co., which produce the show, have lobbied for another timeslot or stunt airings to generate sampling. The only timeslot, however, would probably be 7 p.m. Sunday, and NBC remains committed to “I Witness Video” there through the fourth quarter because the reality hour can be snipped to accommodate football overruns. Separately, NBC will try to boost some of its comedies Dec. 23 with an all-sitcom Thursday, featuring “Seinfeld,”"The John Larroquette Show,”"Frasier” and “Cafe Americain” from 9-11 p.m.