The wheels don't sit in from the arches much on these cars anyway and the arch is a long way away from the wheel so don't personally see the need for spacers. And unless you plan to lower the car and bring the wheels up to the arches then i think arch extensions will look a little silly on a CX-5 but each to their own i guess...
You may find with spacers fitted that the car will try to follow lines on the road more because of the offset change. Don't know how much you know about spacers, but if you buy plain spacers then you will probably need to replace the studs in the hub with correspondingly longer ones. If you go for hubcentric ones then you will obviously need to make sure they come as i kit with all the extra bolts etc... I would also suggest you make sure you buy high quality new ones as i have seen several fail in the past in groups i am a member of because they bought used ones and someone had skimmed them down or they bought low quality ones and they had not been of sufficient strength. You should be fine with H&R as they are a well respected brand. Another that is used frequently on the TT groups i am a member of is MTec.
