Setting up runways in FMB?

[Rattlehead]

I'm currently trying to set up multiple runways on the same airfield in the FMB, with limited success.

I can create the airdromes with their runways simply enough, but I'm running into some issues.

Firstly, what is the airdrome point for? (It always gets created with the airdrome by default.)

Secondly, it looks like airdromes cannot overlap, or else planes spawn on top of each other and blow up. Can somebody confirm that please?

Thirdly, is is neccessary that the take off icon for planes be placed within the runway rectangle?

Lastly, it seems that sometimes planes do not spawn within the runway rectangle, but rather on the default runway.
How can I stop this from happening?

Thanks for any help.