I'm sort of finding what others have found. I started with the run walk method then ran my first race (10-mile) and just ran the whole thing because no one else was walking. I noticed while training that I just ran slightly faster during the interval and achieved the same time. For the half I ran the whole thing and walked through the water stations.
An important thing to remember is that stylistically how you choose to train should also determine how you should race. If you train with run/walk using a Galloway plan, then I urge you to also race using a run/walk using a very similar (preferably the same) interval breakdown. Don't worry so much about the people around you and what they're doing. Worry about seeing them at the finish line when you can hive-five each other on your great accomplishment.
The reason you want to race as you train is because of how the body adapts to the training. By using a run/walk training system you will get very good at run/walk. You will improve your lactate threshold clearance allowing you to run longer distances. But if you choose to continuous run during the race, or choose to change your intervals, then you're no longer using the skill set you trained for. Now you instead are using muscles differently, not allowing rest, and relying on your running economy (or ability to maintain your lactate threshold at a set pace). Because these things haven't been maximized during training then you might not do as well on race day (especially in a marathon) as you could if you just stick to what your training adapted your body to.
I can already tell that it would be almost impossible to improve your time with a plan likke his.
It's possible that based on your running characteristics his plan might not be for you (or stylistically run/walk). But as
@Keels said, it would be best to continue using the plan as Galloway developed since that's what you've been adapting your body to (and thus maximizing your skill set). If you choose to try something else for your next race so be it.
However, on a more global scale. A plan like Galloway's (or a run/walk method) is definitely appropriate for a subset of the running community and they can definitely improve their times. More specifically someone who is really good at lactate threshold clearance as a unique characteristic of their running can flourish using a run/walk method. One reason is because there are some people that have a certain muscle fiber make-up that makes them much better at speed (just one reason). This speed can be used in short bursts (30 sec, 60 sec, 180 sec, etc.) and then during the walk, they have the special ability to drop their lactate levels (a marker for fatigue) to a much lower amount then some other runners. This enables them to be able to go into a speed session again. Whereas, if they changed to a continuous running style they may find they aren't as characteristically setup for it (based on muscle fibers and other physical properties).
I'm starting to plateau now at about 9:30/mi for the looong runs and 9:00 for half or less.
This is a very important point. If I am interpreting this correctly (and by all means correct me if I'm not), then you're judging your improvement (or the plateau) on the ability to run your long run at a 9:30 min/mile. Just remember that the intent of the long run is not to see how fast you can run that distance. It's to train and adapt your body to the needs it will need to run 26.2 miles. For example, you say you are roughly a 9:00 min/mile Half-Marathoner. Thus, per McMillan:
You can see that your estimated marathon time is 9:29 (4:08:20). Now, it's your first marathon so I wouldn't worry about the actual race day finish time as much as completion. But the important part about this number is for training purposes. As I said in my original reply, I'm a big believer that pace is a very important determinant as to whether something is appropriate. Per Galloway's instructions provided in the WDW marathon plan, you are to run the long run "at least 2 min slower than goal pace". Thus, you should be doing your long run at a 11:29 min/mile or slower. You might think, well I "can" run it faster. Yes, you can. And you will on race day. But for the purpose of training it's important to remember that we aren't "racing" during training. We're providing a stimulus to the body that causes an adaptation to allow you to run/walk a 9:29 min/mile for 26.2 miles. So if you take one message away from me it's to follow Galloway's instructions for his plan's long run. Which means you should run a 11:29 min/mile during long run training. Just so you know his "2 min slower" recommendation on long runs is not unique to him. All plans you find will suggest training at a slower pace during the long run so that it elicits the correct benefit (and adaptations).
What will happen if you train at a 9:30 min/mile long run? You would think well then this will make me faster. Not so much. It will cause you to continuously "race" the weekend training run. You'll be able to complete the 17 miler, the 20 miler, the 23 miler, but you very likely will find the fatigue to start to build. On race day it might not go as well as you had hoped merely because you elicited a large amount of fatigue from these training runs that you can't overcome on race day. This isn't because the mileage is inappropriate necessarily, but because the pace you trained at them would be.
To be honest ,I'm finding the mental part of this just as fun/challenging as the physical. You don't really realize all the effort that goes into it outside the actual running. THANKS for all the feedback.
Happy to help!