Be careful when you give advice based on your own personal experiences. It can be helpful but it does not cover all circumstances.
May I?
#2: Not taking Primer first
Without mentoring you should probably take Primer as an entry level introduction to GUE diving and the standards and spend time time with an instructor. This class is currently the best kept secret in GUE, but utilizing it would likely prevent a lot of frustration with fundamentals. If you are already diving with a lot of DIR/GUE trained divers you can probably skip the Primer, but otherwise Primer is likely a better idea.
Sorry - I haven't ever taught a primer and it is simply not
necessary. That does not mean it is not a good class but it is certainly not a pre-requisite to Fundamentals and should not be thought of in that way.
#6: Taking a 6-person course
While the standards allow for a 6-person course, this creates logistical issues, and I'd warn students away from signing up for courses this size. A 4-person course in 2 teams of 2 works well, particularly when there's a tech-oriented team and a rec-oriented team, otherwise the sweet spot is the 3-person course made up of students at roughly the same level.
I could take quite a lot of offence that you are presuming that all instructors who accept more than 4 students on to a class are automatically giving them less.
Think about it - if you have two teams of two in water then you, as instructor can only spend half your inwater time with each team when we move to individual skills. (A good instructor can achieve better than this but the premise stands)
When you move to more than 4 you have to double dive. This may mean that people are sitting on the side but when they are in water they get 100 per cent attention from the instructor.
A well organised class has surface support watching students gear up and de kit, leaving the instructor to dive back to back - meaning that the students 'waste' only the time it takes to dress or undress after the dive - and perhaps get a drink. This you dismiss as 'unprofessional?'
#7: Not thinking your buddies experience levels matter
The other students in the course will affect your success and you should make sure that you're not the odd one out. Having courses with 2 students that are relatively new and rec-oriented with one tech-oriented student, or vice-versa can be hard on the course. Its best if there's someone there diving the same gear with roughly the same experience and goals.
I'm sorry - again that takes the view that an instructor is unable to ensure that every student gest the chance to be the best that they can be. If an instructor cannot do that then they have no business teaching.
We are talking Fundamentals here - if I have a diver who can earn a tech pass who has buddies that are not up to that standard then I will buddy him with the video diver or even take part in drills with him myself to ensure that he gets every opportunity. Tech or cave classes may be team dependant but Fundamentals is not.
#10: 5 straight days vs. split courses
With a local instructor one option is to do a split-weekend course with 2 or 3 weekends 'off' in the middle to practice. This can greatly reduce burnout and can let the student get in some solid diving outside of class to brush up on skills. Obviously, this is only an option with a reasonably local instructor. If you are flying in to the course or the instructor is flying in to the course this isn't going to be available to you.
I've taught both. The split class wastes time, the momentum is lost and the day on day progression can take a step backwards. The instructor has to get the class to a point where you can go practice. It kinda forces a 5 day class just to cope with the re-caps and performance deterioration incurred.
It can work. It can fail - you just can't make bold statements that one is better than another.
In summary - many your points which I have not commented on (like talking to your instructor, not using new gear, not aiming for a tech pass, getting good rest and nutrition, keeping shorter days) I do agree with, but I worry that threads like this end up making people feel that they will not be good enough so they don't book on. It is not basic training for marines - it is a diving class and a professional instructor will have considered the logistics well.
I have had a student with 15 dives pass fundamentals (rec pass, wet suit in warm water). I have had people dive doubles on the class for the first time (I don't advise this) and get a solid tech pass. I have run 6 person classes where students have had 6 dives long each with my full attenion (my favoured class size is still 3) and I have had a full on hurricane in the middle of a four day foreign class which ened up with us doing search and rescue overnight and reduced my inwater days to 2 - a class we still finished successfully for those involved.