Mating slugs

I know PZ has recently posted a picture and a video of slugs mating. But these pictures were taken here in North Carolina, by blog reader Kris Barstow, who says:

The year was 1999 plus or minus a year, the site was a few miles from Asheboro, NC. I don't recall the season, but it was warm, and there is definitely a chill there in the cold seasons, so I assume spring or summer. It was about half an hour after sunrise; I was walking my dog. I would occasionally carry my camera "just because ..."

I saw these two acting strangely on the surface of the wooden shed. They actually attached themselves, then went into freefall. They twined around each other, and then a moist pouch was extruded below them. White froth was present but in moderation.

I don't recall what exactly happened after that. They remained suspended for some time, and the likeliest thing is that I left them to their passion.

i-9dac931df8029b6c9049552a20a7bc81-SlugLove1.jpg
i-c37d441bf63eb0781dbd1b1e012b305a-SlogLove2.jpg
i-b429ff12f6917c03569a6fcdaea2b5d5-SlugLove3.jpg
i-836cad4c28dc7d851c96e4557c3a67fb-SlugLove4.jpg

So, can someone identify the species?

More like this

How big are they? Limax maximus mates dangling from a mucous thread like that. Adults are about thumb sized.

I would have pegged them as Limax maximus because of that acrobatic behaviour. Haven't seen them that colour before so they may be something else. The ones I see in my garden here in southern Australia are usually more grey and black.