I'm looking to buy a set of X6 style 232 wheels for my 08 X5. From what I've been reading, the rears will not fit unless I use spacers or bore the wheels to 74mm. Does anyone have suggestions on what's the best and safest approach. If I were to use spacers, would the 15mm be better than the 20mm since it's not as thick. I know with the 20mm spacers, they provide additional bolts. I'm trying to go with the safest route. Thank you.