I am in the process of upgrading from the standard 16" alloys to 19" Sport alloys. I understand that spigot spacers and new wheel nuts are required, but what is the general consensus on spare wheels? I only have 4 Sport alloys, so do I carry my original P38 spare + wheel nuts and hope that I can remove the spigot spacer or do I need to get a fifth Sport alloy? Does this alloy fit under the spare wheel cover? And finally, is there a noticeable rolling radius difference between the alloys preventing me from mixing wheel sets on the same axle? I know that I could answer many of these questions myself by just going out and trying these things, but my P38 is currently stuck at work with a flat battery!