Wow, lots of advice from lots of people! Thanks everybody!
Let me first say that the plan that I had came from more than a few hours of practice. I find that the other cars start pitting at 23 laps, and I can manage exactly 23 laps that are around my target time on one set of racing softs.
Let me also apologize, because maybe I wasn't clear. I'm using the EPSON NSX, not the street NSX.
My goal
is to get the 'real endurance experience'. That's the main reason I'm asking for your help, because this is the first time in an endurance that I'm using a car that is less powerful and slightly heavier than the 'rabbit' car.
Check which cars are entering, take the same as one of them (or the same as the rabbit car if there is one), undertune it or use tyres that are worse, and try to make the tyres last a lap longer as they do.
That's my strategy at least
I couldn't find a SUPER GT car, but I did find three other racing spec NSX's lower in the grid, so that's why I figured I'd use this car.
The most interesting thing to me about your comment is the 'make the tires last a lap longer' advice. Is that because you always want to have better tires than the competition? Or are you aiming for one fewer pit stop than the other cars?
I'll definitely give this a try today.
To get the "real" endurance experience, check the opposing car list for the event and choose a car within the range of PP. Then use tires that correspond to the car's type (race car, street car, etc).
-Use street tires if you can, as they last longer than racing tires on lower performance cars (pretty much anything that isn't a race car, but use your judgement). They have more understeer, which is the downside to them.
-Drive a practice stint in practice mode or in the race itself. The tires always (I think) run out faster than the the fuel. Calculate how much fuel you use in a stint and add a certain amount each time so you run will run out of tire grip just as you are getting low on fuel. This will make pit stops shorter as you will spend less time refuling the car.
-Don't push your car too hard. This will decrease tire life.
I would consider this car a 'racing car', and I think that if I use tires any worse than these, I'll fall to the back of the pack in no time flat. I'm going to be running a bunch of practice stints today if possible, so I'll still give this a try.
Your fuel advice is something that I certainly
will take, though, because I've been filling my tank every time. Also, is the weight of the fuel a factor in Gran Turismo physics? Just another possible added benefit
The conservative driving thing is perhaps the biggest lesson I had to learn for this race. Before I started slowing down and pacing myself, I was getting no more than 13 laps out of these tires!
so youre using a stock tuning setup [horrible] with racing softs [horrible]. I wouldnt have a minute of fun if i did that. grab a tuning setup and use racing hards, your laptimes shouldnt drop off since the car is underpowered anyways.
Actually, the challenge provided by an underpowered, overweight car tuned to near-real-life specifications, where the only benefit I have is more grip than my competitors has proven to be an intriguing, and rather entertaining challenge for me.
I set tc to 3 or 4, this helps conserve tyres by reducing any wheel spin, I don't use tc normally just in endurance races.
This makes a lot of sense, but I'm adding this element of challenge to my race.
If you go to it and it's raining leave and try again. If its raining or rains during the race it can add an extra 2hours or so to your overall time :/
Aww, but where's the fun in playing God?

Fortunately I won't be under any real time constraints tomorrow, so an extra two hours won't kill me.
I'd say don't get too tied up in how many laps you want to achieve in a stint just pit as soon as you feel the tyres considerably wearing. That way you should have more concentration on your whole stint rather than worrying how little grip you tyres have towards the end of a longer stint where the chance of making a mistake increases as well.
Hmm, this strategy is in direct contrast with the first one, but two of you mention it. I assume you're suggesting pushing the car as hard as possible, as well?
With this car, since I don't forsee gaining a full minute lead on the competition in 13 laps, the only benefit I can really see for this strategy is the ability to go slightly faster and shorter pit stops. But wouldn't doubling the number of pit stops really limit those benefits?
Again, everyone, thank you for all the advice! Anyone else have tips for me?