Sure. The onyl
reason to have it well-centred it to improve mechanical
 balance and reduce vibration. 
 Whats the track width on an RK05, I semm to recall its 100TPI so thats  
 
I think it is, indeed, around 100 tpi
  10thou per trak, add a bit of guard space so maybee
8thou track width ?  if
 you have 1 or 2 thou exentricity ok, more and could lead to
 interchangability problems ?, mind you 4 thou out may meen its vibrating so
 badly   that this is the least of your problems. 
No. Remember the hub remains fixed to the platter when youremove or
insert a cartridge. So if the platter is off-centre, the tracks will
remains cirles, i nthe right places relative to the centre of the hub.
The fact that they are not concentric with the outside edge of the
platter doesn't matter at all
-tony