Getting ready to order some replacements, but I don't see any exact matches. Some places say to measure from the bottom of the seat to the bottom of the bolt (27mm), and some say to measure usable thread (22mm). Which is it?

 

I'd say thats a stock 996/986 length 27mm

 

I ask my wife that very question from time to time....

 

Have your parts store look up a lug bolt replacement for length. I just had to look mine up but can't remember thread specs.

 

@sshrum - I knew someone would go there

I would get the stock replacements, however I've got aftermarket wheels and wanted to make sure before I bought those shiny titanium lugs.

I'm also in the 27mm camp, 2mm too long couldn't hurt - right?

 

Yes, it might. If a lugbolt is too long, it tightens up against the hub and not your wheel leaving the wheel to wobble about on the lugbolt.
Not saying that this will happen in your case, but if the bolts are currently very close to the hub, 2mm may be the difference between it tightening properly, or leaving 1-2mm wobble room.