To report back on lowering my standard suspension 660Z here in S Africa. (I'm moving to Aus early next year and the links are actually for my 660Z there which has Teknik off road suspension front and rear).
I have 2 sets of lowering links now - for 1" drop (133mm hole to hole centre) and for just over 2" drop (140mm hole to hole).
Fitted the longer ones and had a trip on the motorway this morning, as well as suburban with speed humps (which I normally take at speed and let the suspension soaks it up). Also set the shock up to the 2nd notch (was on weakest setting).

First of all, it tamed the bike considerably. I'm 1.79m (5'10") tall and my feet are about flat on the ground where previously I was on my toes. The excitement was a bit subdued in riding feeling, but it's really much easier to ride. It doesn't want to tilt over so easily when stopping - centre of gravity is lower.
I think it will be much easier to control in tricky situations (like off road).
The steering and balance was easily adapted to and no problem. The feeling on the road was the same when turning.
The chain rides tighter but is fine. Haven't checked the underside of the swing arm but I'm sure it will be fine.

I found three slight disadvantages:
The bike stands very upright on the side stand (left standard length) and one has to check where you park before you get off. Same with stepping on the foot peg when getting on while on side stand.
The suspension feels "shorter". Not that lovely long suspension that you can take over the worst bumps at speed.
Lastly I hit some speed bumps at high speed and back at home saw that the back wheel had touched the cross pipe of the Scorpion exhausts. When on side stand the tyre is only 10cm from that pipe. I'll turn the suspension stiffness up a bit still. But twin pipe exhausts should be taken into consideration when lowering it this low.

Next I'll replace the 2" drop links with the 1" links and evaluate them. I have a feeling they will be a better compromise on this bike - as long as my feet are a bit more secure on the ground than just the tippy toes as with the standard links.

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2014 XT660Z - Barrett pipe, DNA stage1.5, Barkbuster hand guards and handlebars, Pivot pegs, Teknik suspension, Guard-it engine protector combo, B&B rear rack, Trax topbox.