No, the box is already present both below and after the front seat. It is fixed into place through some studs on the floor, so no sliding.
I have no idea what it's like for adults to sit with their feet raised, but with the box in place that's the only way to sit.
Or remove the entire box when you expect adults in the car. However, that probably involves sliding the front seat forward and putting the clunky box in the back somewhere. The only bonus then, is the fact that the box comes with such a nice carrying handle.
BTW: I do not have the space floor box on my own A2, but had one on a temp A2 I took for a holiday to France. I left the box at home...
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(2003 Silver 1.4 Tdi Exclusive(SE), 95bhp/235Nm chiptuned by ABT, black interior, sport seats, heated mirrors, JVC KD-SH909RB cd-receiver, Infinity Kappa 63.1 + Vifa on-dash tweeters, 12" Subwoofer on 300w Amp)