Heaven help me - I've just bought a delta kit :-)

[curious aardvark]

my retraction settings are 1.8mm and 60mm/s.
Retraction distance isn't as important as the speed and making sure the slicer actually does use retraction any time it crosses any open space. Also found that making it retract between layers also helps.

It's making sure s3d retracts every time it crosses open space that's the only issue. Should have that cracked with current print. Set minimum distance before retraction to 1mm. (yep I can hear the difference, way more 'zzzppp' retract noises).
If I print more than one object at a time there is absolutely no stringing between models.
High travel speed seems to help as well.
Although that's curently only set to 100mm/s.

Don't think that gap is an issue. Given how well she prints, I'm not going to mess with the arms :-)