Reliable sources are telling me that the Wednesday opening for Ben Stiller’s Tropic Thunder from DreamWorks/Paramount was just around $6.5 million from 3,319 North American theaters. (But another R-rated comedy, Sony’s Pineapple Express, did $12.1M a week ago.) So what are its weekend prospects? Well, the studio fully anticipated the soft Wednesday opening and still believes Tropic Thunder can make $40 million in its first 5 days. “We will play to a little older audience than Pineapple Express, so we should do better on Saturday and get to about the same box office,” one insider tells me. But one problem is that, unlike Judd Apatow movies, Tropic Thunder has underweighted wanna-see among the gals: there’s only moderate interest among women under 25, and zilch interest among women under 25. Another worry is that this was a very expensive laugher, witha negative cost of $100+M. To get to $40M domestic gross, the studio is hoping that the old maxim holds true: that any publicity is good publicity. And this pic starring Stiller, Jack Black and Robert Downey Jr has been hyped to the max. On the down side, some vocal African-American actors (because of Downey in blackface) and mental disability advocates (because of the un-PC use of the term “retard”) are pissed at the spoof. On the up side, critics are loving Ben Stiller’s direction and script and story (with Justin Theroux) and Tom Cruise’s cameo. But all along Hollywood has wondered whether Tropic Thunder could break the curse that movies about movies don’t do well at the box office, especially if they’re stuffed like this one with the kind of insider jokes that would even go over the heads of The Grill’s lunchtime regulars.

Here is what my box office gurus are predicting: low $30sM for Friday-Saturday-Sunday and low $40sM for the 5 days. As one of my experts analyzes, “Unfortunately, a few of the tracking services say that Tropic won’t be as high as Pineapple. They are saying about $35M for the 5 days. My gut is higher. I bet $42M for the 5 days. The reviews could not be better, the heat is huge, people love comedy. I think it will surprise.”

As for this coming weekend’s Friday opening movies, my box office gurus are all over the map on LucasFilm/Warner Bros’ Star Wars: The Clone Wars toon for the geek in all of you (not me) with dominant tracking interest from males over 25, with predictions from a low of $15M to a high of low $20sM from 3,300+ venues. The higher numbers depend on how many 8 to 11 aged boys show up to see it. Mirrors, the Regency/Fox horror film from the director of The Hills Have Eyes and starring Kiefer Sutherland, will probably open in the low teens with around $13M with balanced interest across 3 of the 4 quadrants. Male over 25 interest is the weakest but appears siphoned by Clone Wars and Tropic Thunder. And Woody Allen’s sexy Vicky Cristina Barcelona from The Weinstein Co/MGM starring Scarlett Johansson, Penelope Cruz and Javier Bardem, should collect about $3 million from its 692 runs. Also opening is Summit Entertainment’s animated feature Fly Me To The Moon which is going out in 3D on every screen (428 real D, 16 IMAX and 8 in Canada). The weekend estimate is $1M to $2M, limited by not by demand because consumers want to see 3D films (ergo the success of Journey To The Center Of The Earth) but by supply within the exhibition community. Summit acquired the rights to the film with no minimum guarantee. And Warner Bros’ mega-blockbuster The Dark Knight? This 5th weekend in theaters will see it drop from No. 1 to #2 or possibly even #3…