Collie:
where you get them from, are they dear, i fancy widening the track on the back of my mk4.
whats the widest i can go without arch work
what suspension are you running again Collie? iirc 30mm or so... in which case 15-20mm will be fine.
i was running 20mm spacers with coilies which was slightly too wide as it was so low(caused rubbing), but its fine for 40mm lowered mk4's
OP, 5mm is slightly pointless like already mentioned 10mm will be nice. eitherway, i would recommend longer bolts. i have 4mm on the front of mine (just to clear coilover) and i can JUST, JUST get away with standard lenght bolts. but 1 year down the road i ended up sheering a bolt in the hub so i would really recommend longer bolts.
Luke