UPDATE:
I am now in designing the last Act missions, Act 4. And if completed, I will still be halfway to finishing the Mod because I have to make Journal System and the images for it, create the Command Briefing static images (one for each), briefing icons, weapon icons, more background images, some music editing, re-edit and modify a Terran Knossos portal from the old Blue Planet (not the BPC version), search for a suitable model for the Portal Control Station and modify it, of course (I might use the Starbase from Star Trek), more modular table adjustments, debugging, gameplay adjustments, and final Beta testings.
There are also some observations I made when using FRED 3.7.2. This might not be true with the latest SCP versions but I'll just mention it all the same. Here are four of them:
First observation and it was CT27 who discovered it for me, I found out that SCP did not factor in the energy-to-engines transfer for afterburners. I made a new fighter with a normal maximum speed of 60 and afterburner of 80. If the player devote all energy to engines, it goes up to 90 (max oclk speed) and pushing afterburners will reduce it to 80. All this time I thought this will change as well. So I have to manually adjust it. One lesson learned and learning will not stop here.
Second. When I design some missions involving the hostiles reacting to your wingmate commands, there is one crucial SEXP that is impossible to set in an Event using the FRED editor - the "Query order" and this happens to be very important. No matter what I do, the option is just greyed out. But I solved it by editing the mission file directly using Notepad and viola! All the "Query order" SEXP arguments are available when editing again in FRED. I hope this is not the case in later SCP versions.
Third. When making skyboxes using sphere models, I have to use textures with huge dimensions around 8192x4096 pixels to render the game background beautifully. This image file will easily have a size of around 60mb (PNG format, DDS files will be larger). Now, the game did not start the mission, the computer hanged. Maybe because I have an average PC. Nevertheless, it's an issue for me so I stick to texture maximum size of 2048x2048 resolution and forgo the usage of Sphere models for skyboxes and use the "tried-and-tested" cube model instead.
And Finally. There is also one bother in how FRED implement the Event Log feature. It automatically assigns or check the log option boxes especially the "True" and "False" boxes and how it sometimes rechecks those options again even after you uncheck them and save the mission. One instance, if you don't notice, the editor checks the options in ALL the events. This would be useful in debugging the mission but I found out that the game updates the event log by the milliseconds (except if you also checked the "First Triggered" option). If you're not careful, this will prick you. Imagine each event line in the mission design with their "true" and/or "false" states written in the log over and over again every millisecond. Then imagine if you have a 15-minute mission and just a 100 mission "Events" in the design. The event.log text file will have 90 million event log records written in it (one event will be written 900,000 times). And what is worse is that EACH recorded event will have a number of text lines that will depend on the kind of event; the basic "When-true-do nothing" event, counting with the "time stamp" line, will have 4. So, 90 million times 4 is 360 million lines in a text file, 3.6 million lines for one event, which will be difficult, if not, impossible for the computer to open - the text file will have a size of around 500 to 700 megabytes. And not considering if you can read all of them; it's a full library! AND here is the worst of it --- While playing the game, your hard drive will be constantly writing! At some point, the game crashed when playing one of my missions and it had 300 mission events, the log options for all events checked. Because of this, I make sure all event log options are unchecked before saving and making sure it stays that way when I re-open the mission file then check the size of the "Event.log" text file in the mod's data folder just in case. The game also ran smoothly when releasing this processing burden from my poor computer. I also noticed some of our popular mods have this "problem" and so I have to edit their mission files.