I figured how to get "RT CDS Seaplane" to work in the game. First, you will need to download "AC Functional Airports Version 1.0". After you have downloaded the Plugin install only the "AC Functional Airports Version 2.1. Go to your Plugins Folder and look for that file. Open it up and remove the Seaports folder and also Revove the "SC4 Functional Airports and the X-Ports Automatic Upgrade".Keep out of the "Airports" folder are "Enable RT CDS Island Air and if you want to have the SG Helipad then Keep the Enable SG Helipad". Reload the folder back into your Plugins (make sure it is the last folder to load), start the game. If you would like Load up a Test Region and place the Plugin in the test Region. I also loaded the "CSK2 Small Port and also PEG-Container Processing Dock" nxt to "RT CDS Seaplane". I saved the game with ctrl-save option. I did this about 1/2 dozen times and the Region opened and no CTD. I've included a pic so you can see what I am talking about.
Just be careful: AC Functional Airports includes an optional "cargo handling facility" that is a landlocked BSC seaport in disguise. BSC seaports don't play nice with PEG seaports without some serious hacking. If you somehow manage to get two conflicting master seaport controllers in the same city, it could become impossible to open or repair.
Thanks for the quick reply jeffryfisher. I removed all the files except for "Enable MOD Helipad, Enable RT Island Air and SG Helipad". I also deleted the "SC4 Functional Airports and the X-Ports Automatic Upgrade" The files I saved and loaded the game and all 3 Plugins are in the game under "Build Airports" close to the top of the menu. By removing all the unwanted Plugins I have never had any conflicts in the game, so far.
Update:
If you do install the "RT CDS Seaplane" in your game it will in time, lock and CTD. I had it installed in my game and was locked out of the region I had it installed in. I thought it all was fine till I tried to open the Region to play. I had earlier opened the same and it loaded fine but not this time it did not, CTD right before the Region would have loaded. I then started the game and checked the test Region I had the plugin installed. The Region opened fine and all the Regions around would load just fine. Went back to the test Region and tried to load it and it CtD after loading fine just a moment ago. So in my findings, DO NOT USE. the info in my first entery. If this has caused anyone problems I am sorry.
Sounds like you found a way to create the competing controller conflict I warned you about.
I know this is an older topic, but if you haven't lost this region, I would suggest installing the latest version of BSC Functional Seaports (https://sc4devotion.com/csxlex/lex_filedesc.php?lotGET=1663) and AC Functional Airports (https://sc4devotion.com/csxlex/lex_filedesc.php?lotGET=1664) and seeing if it helps restore your locked cities.
Both of the PEG seaports you listed are supported, and the BSC Seaport controller works perfectly with the AC Functional Airports. I do recommend using the included Cleanitol files, to remove all conflicts before attempting to load the region though.