Just undo the bolts at the front and stick one or two M8 nuts between the tank and frame on each side
You could use pretty much anything that physically fits over the bolts- door stoppers are a popular choice I think, washers, bits of wood, but pretty much everyone has a couple of M8 or similiar nuts lying about so I only mentioned them... You might need longer bolts too. Seems like about 15mm is as much as makes any difference.
The Renegade airkit makes a difference to the sound.... Personally I don't consider it a particularily good filter job but the flat filter does definately boost the induction noise, so if that's what you're after it'd be a much better choice than it is if you're after performance. I've got a spare Renegade filter somewhere and maybe the jets, you could give those a go.