Ian, Sorry to hear you and others are having trouble. When I first converted the Leander's, Tiger's and County's to FS9 I certainly had problems with the County class. I do not remember getting a CTD, but I could not get them placed using either Instant Scenery or EZ Scenery. The solution was to reduce the number of polygons in the Sea Slug missiles. I originally had these as 32 facet tubes, and reduced this considerably, together with some of the surrounding ironmongery. I can only guess that FS9 did not like that number of polygons in a small volume. I am afraid that I have no answer as I can place all three classes successfully in FS9 using Instant Scenery. If someone can identify something in the model that is causing your CDT I am more than willing to try and rectify it.
For your information I create the models using FSDS 3.5.1. I then load them into FSDS 3, remove the attach points for the nav lights, steam and wake, and change the radar animations to Tick18. Then compile the mdl using the FS2004 SDK if there is no flight deck. For those with a flight deck I output an x file from FSDS, add the necessary lines for a "PLATFORM_CONCRETE_0", and use "makemdl.exe" (FS2004 SDK) to create the mdl. The bgl is created using the library maker from Instant Scenery via the FS2004 SDK.