Dual question - launching satellites and nebulae

[Growltigga]

I have a couple of questions for you experts, one specific, one general:

1 I am trying to place sensor buoys with stealth armour I on the frontier warp points of my empire. The idea is that these buoys, when cloaked, can just sit there and give me advance warning of any hostile intrusion by the AI. The problem is I only need to lay 1 buoy per warp point. I have a satellite layer based on a destroyer hull with only 1 satellite launch bay but on simultaneous play, the launch units order button will automatically lay 2 buoys - talk about redundancy - can anyone tell me if it is possible to lay only 1 buoy and 1 buoy only short of only carrying 1 buoy on the ship??!!

2 I am playing on a large ancient map, the borders of my empire comprise lots of nebula systems. I have placed my sensor buoys on the warp points of those systems but these do not pick up transit through said warp points by any hostile vessels and once the AI vessel gets into the nebula, it disappears - is there any way of placing detecting transit of hostile vessels into a nebula system, short of mining the exit wp's?