I am looking at buying a set of LMGT4's and have found some with the sizes: 
  
Front: 17 x 7.5 offset +30mm 5 x 114.3 
Rear: 17 x 8.5 offset +40mm 5 x 114.3 
  
Basically i do not have a clue about wheel sizes, offsets etc and was hoping someone who does could help me out with two questions. 
  
First question i have not seen anyone with 17's on here everyone seems to have 18's or 19's, will 17's be ok and how do you think they will look? 
  
Secondly i tried using an offset calculator which gave me: 
  
Front: Inner Clearance; 6mm more  Outer Position; retract by 6mm 
  
Rear:Inner Clearance; 16mm less  Outer Position; retract by 4mm 
  
Does this mean i need spacers and if so what size? 
  
As i said i have no clue about things like this. Thanks.