The inside tread of both back tires is wearing quicker than the outside. Is this a camber adjustment that needs to be made? How hard is this to do without making things worse?

sounds like you have too much pressure in your tires ... i had the same problem before

i read it wrong .. my mistake .. i read it as middle of tire ... yes it is definately the negative camber

Now wait a minute... It may be a case of not going corners
fast enough!
Joe

Exactly! Need to do more twisty, and less straight-line, driving.

The standard factory alignment has negative rear camber. More wear on the inside is normal on a turbo.