You can do new ships appear in convoys by deleting the line of the class=.... of the RND file. It is a little bit timming procedure (30mins) but very secure! In the ubi-SH3 forum we have analized it two or three times and everybody is pleased with the result! Personaly I have removed the C2 (KLS)-small merchants(KSS)-tramp steamers (KSQ ). Use the function Replace-With of the Edit MENU by openning the RND file with wordpad. e.g. Replace: class=KSQ
With : (BLANK).
This will empty all the class=KSQ lines from the file and everytime the game code loads that part, the choise will be generic according to the designation of the type. E.g type=102 (merchant) any merchant is available. If you do it with liners (103) any liner will be available.
This procedure is garantied!