The PET says that they are 6x12's but is there a special pitch to them? The standard 6x12's that I have are course thread (i.e. #1) and seem to bind up just as they go in. Are they a 1.25 or 1 5 thread pitch or do I need to clean out the receiving nuts in the longs?

Someone may jump in but I believe they are the same small"bolts" as the sheet metal screws for the engine tin.

They are standard VW /Porsche cheese head screws.
Yes, clean the threads before attempting to install.
Often it is difficult to get the screws to start straight into the body nut.....
... so they get cross threaded
pic of proper hardware AFAIK

They are course thread, at least mine are now. I was fighting with mine yesterday. I had to chase the threads with a tap to get them in.

Same screws as used in the engine tin. The stainless Allen's we sell work well here too. Much harder to strip while removing. PS a vice-grip with a screwdriver can help to remove stubborn ones

Thanks Mark, just grabbed some!

No problem, your welcome.