What size bolts hold the systems together? I have to take mine apart to fix a few things and the bolts on there are not going to cooperate, in fact I'm not bothering with spanners, going in with the angle grinder to get it apart (the really are that bad) however I need to know what size bolts to buy when I am ready to put it back together. I am on about the bolts holding the centre box to the front and tail pipes