Right. OK so far.

I'll explain the procedure for any FS2000 aircraft in CFS2. First, you need to convert it to carry external payloads. Download the MDL Converter tool here.
http://www.simviation.com/cfs2utilities1.htmRun the converter & patch the MDL file of the new aircraft. This is simple enough but don't use the Optimize Graphics option.
Now you need a DP file to work with. Copy/Paste a DP file from any default aircraft into the main folder of your new aircraft. Rename it using the same file prefix as the AIR file in with it.
Be careful to use the exact file name or it won't work. The new aircraft will now use this DP. You can modify it with DPED Version 1.10.
This is posted on the same page as the MDL Converter.Each time you modify a DP file, delete the corresponding CDP file before trying it in CFS2.