OK so I am not particularly savvy on the technical stuff- so I apologise in advance - but I don't understand this issue of the Spacer ?
People are saying here that the spacer simply raises the seat height - and this makes sense to me - so I would not expect this to affect the chain tension (i.e. seat is moving upwards but surely nothing else moves ??).
Having said that - I am aware from my bike that having a spacer fitted means that on the centre stand - the rear tyre does almost touch the ground, when on a standard bike there would be half an inch clearance - so clearly something is going on ? So my guess is that fitting the spacer means the swinging arm is being forced downwards based on the new longer length of the shock ?
So this must mean that with the bike on C/stand - the swing-arm is sat lower than horizontal (or lower than it would be on a standard bike) - and so more "slack" is provided in that position ?
I guess the only question left on this is "....so how much SLACK is considered correct when you get the chain and cogs in line ? Someone mentioned 5mm in an earlier post - someone else said 18mm - and my recent guess was 20mm.....