Based on the discussion in the personal testing thread, I have the following, which is more closely aligned to how the ballast actually worked in netKar:

Here is a range of cars that gives a good spread of average lap times (include the BMW M3 and 1M in place of the Z4s, as per Marty's suggestion). The gap shows the gap to the previous car, just to show that it's a good spacing of times, with no two cars being too similar to another (does fall off the cliff a bit with the Z4, but it doesn't matter, as we shall see). The Cumulative column shows how many seconds that car is slower than the baseline, the Exige 240R s3.

 

Car	Avg	Gap	Cumulative
Exige 240R s3	118.81		0.00
Evora S S2	119.27	0.46	0.46
Exige Scura	119.62	0.35	0.81
Exige S Roadster	119.96	0.34	1.15
M3 E92 Step 1	120.53	0.58	1.73
Evora S	120.88	0.34	2.07
Exige 240R	121.06	0.19	2.25
BMW 1M	121.56	0.50	2.75
Elise SC S2	122.31	0.75	3.50
Elise SC S1	122.80	0.49	3.99
Elise SC	123.34	0.55	4.54
Z4 E89 S1	124.83	1.48	6.02
Z4 E89	126.49	1.66	7.68

Now if we look at drivers' fastest race laps (this is from Monza), we can see how much slower each driver has to go to be on a par with the slowest (Gap to Slowest). Using that gap as a lookup into the table above, you can work out which car will make Guybrush roughly the same speed as Imperious - the Elise SC, which will slow him down by 4.54 seconds (actually leave him a little bit quicker than Imperious - but that's his payback for being skilled). Do this all the way down the list, and the lap times will be much closer. I would base it on the average of your fastest laps over the round. The baseline car that everyone would start in then is the fastest - the Exige 240R s3.

 

Driver	Fastest Lap	Gap to slowest	Car
Guybrush Threepwood [Achilles Heels]	112.324	5.66	Elise SC
Marty [Achilles Heels]	113.235	4.75	Elise SC
StanDaam [XGN]	114.332	3.66	Elise SC S2
Wally [TKO Racing]	114.469	3.52	BMW 1M
Ysu [TKO Racing]	114.611	3.38	BMW 1M
Freezer [XGN]	114.800	3.19	BMW 1M
Rob [Team MRT]	114.863	3.13	BMW 1M
cramjet [CramDick Racing]	115.277	2.71	Exige 240R
Glen73 [Projekt Rennesport]	115.294	2.69	Exige 240R
Rolz [XGN]	115.321	2.67	Exige 240R
Bacchulum [Aleph Null Ltd]	115.327	2.66	Exige 240R
Gratulin [XGN]	115.487	2.50	Exige 240R
Crimespree [XGN]	115.649	2.34	Exige 240R
Grubbet [XGN]	115.749	2.24	Evora S
Dave O [XGN]	115.956	2.03	M3 E92 Step 1
Vipergod [Team MRT]	116.236	1.75	M3 E92 Step 2
Dick Forrest [CramDick Racing]	117.784	0.20	Exige 240R s3
Imperious [XGN]	117.988	0.00	Exige 240R s3

Fine print: you have to scale this by the track's lap time - e.g. just because Guybrush was 5.66 secs faster at a long track like Monza, doesn't mean he would be 5.66 secs faster at Tsukuba, or some other much shorter track. If the next track was Tsukuba, Guybrush wouldn't have to be slowed down as much. This is what I did with the netKar ballast too.

It was a lot of fun. In race 1 I made lots of mistakes (i.e. spins) but in race 2 I tried to be more consistent and had no real dramas to come second. Favourite turn - the right hand sweeper at the end of the straight, with the rear end threatening to break loose at any moment.

Well we had a bit of a discussion about it last night after the Cobra races.

It was fun last night, in a bit of muck around racing, with a mix of cars with different strengths and weaknesses. It does seem though, that the BMW's are a little too outclassed. I probably will ditch them from the mix.

Also, because car selection should be based on speed and not other factors like racecraft, what I think I'll do is assign a separate leaderboard sorted by fastest race laps as well, not for points but just to assign cars. I.e. You get points 24 down to 1 in order of lap times, and then the leader of that gets the slowest car etc.

Wally thats awesome, can you just make my font in bold please. I cant see it properly amongst the others 

Seriously, does your boss know what REALLY happens at work?

You mean my wife who wants me to paint the bedroom while I'm on holidays?

Thanks to Wally's seemingly endless patience and Birds assistance, the server is configured with all the races in the signup thread head.
The server is telling me it is running okay.
I will not be home till ~7 and will join ASAP.
If anyone can check earlier, espesh if you have skin loaded. great.

If all fails we will use Wally's server with random skins. (Okay Wally? )

OK. If all else fails. PM me your server_cfg and your entry_list and I'll be able to make it exactly the same as your config.

I missed all that. What was the track that played up?

Mid Ohio.

No seems all cars are selectable there didnt seem to be one assigned to me. In the lobby it said to select car so I first tried the standard then the s1. I even jumped into a lotus to see if the performance issues could be due to more cars then grid spots but the last elise in the list loaded in pit fine.

Oh, that's not how I thought it worked then. You do have a particular model assigned to you in the entry list (the standard Z4).