Banners fluttering in the slipstream...I did indeed spend many a head scratching night trying to figure out both this dilemma, and more importantly, how to unfurl a banner when I was contemplating doing this on a B.2 model. In the end I learned that you cannot scale anims in the FS9, only FSX. This was a major hassle when I did the TT.18 with its Rushton pods - I wanted to have tons and tons of cable length pay out from the winches and was going to use scale for this, alas it was not to be, but thanks to Dave Garwood over at CBFSIM for the idea of 'telescoping' the cable out instead. Not miles and miles mind you, as it was hassle enough to pay out even 100 odd ft of it!
Back to the fluttering though - someone apparently has done it on a Spirit of St. Louis model, I never did check it out though. If it can be done, rest assured there will be target tug models for both British and US B-57s made in future.