THERE IS ONLY ONE SIGHT ... The "Dot 'O Death" sight ...
Here are the sights that I use. They are alpha (illuminated) sights.
You place both the ???.bmp and ???_alpha.bmp into the HTC\Aces High II\sights directory and when choosing the sight in AH setup, you chose the ???.bmp
You might want to backup your \sights directory before making any changes.
Fighter: Carefull here because it is named "default". This should automatically change all plane gunsights to this sight without a lot of effort.

<- default.bmp

<- default_alpha.bmp.bmp
Jabo: For this sight I explicitly go into the AH setup and choose this one for all the planes that I use for JABO. The bottom dot is what I use to line up the bomb drop on. Usually try to get 45 degree angle on drop using the lower dot.

<- default2.bmp

<- default2_alpha.bmp.bmp
Credit here to Mitsu's buddy AERO. I took one of his sights and modified it.