I was planning on making another batch of weizen soon. Over on the HBD board I saw Chris White recommends 5-7m/ml for a weizen. I've never tried pitching one that low, or as high as what Narziss recommends. It sounds like an experiment is in order. It wouldn't be too hard to do a split batch and see which one turns out better.
It would be interesting to further split things out and ferment each of them at different temps. It would be nice to see what makes a bigger difference - temperature or pitching rate, and also whether the two are additive or whether you max out on phenols or esters at a certain point.
FWIW - I typically pitch 1 smackpack of 3638 with no starter for a 5-gallon batch of a 1.050ish weizen, which is right at the lower end of the range Chris White gives. Fermenting at 64-65 gives some real nice phenols (clove with a bit of cinnamon/vanilla) but the banana is still there. I couldn't keep the temp down as well as I wanted on my last batch and it ended up fermenting at 68F. I lost most of the phenols, but didn't get as much banana as I would have liked either. These have all been extract batches, so YMMV.