As long as he puts P Zero's on i'd let him do it - You'd be looking at around £90 a tyre fitted depending where you go but it's just extra hassle you don't need!
Or second thoughts, take the money off (ask for £200 for the hassle) and put it towards a set of 18's anyway?? I had mine refurbed (powder coated) and they look awesome now, will grab a pic
