[Purist]

Every major series that comes to mind (F1 and Grand-Am mainly) that used the layout with Oval Turn 1 also used the Turn 5-7 loop in the infield, so I just put the two pieces together by default. That layout is officially listed as 2.534 miles, though with the smoothing of the esse before the track heads back on to the oval for the 2015 season, it's marginally shorter, so should be something like 2.530 miles.

Check the SC365 piece linked to in the opening thread post about the Las Vegas course layout. Of note is the part that they looked at a number of different configurations. So it seems there's nothing officially ruling out using banked turns (and Indy's are low compared to most top-tier ovals). However, it also makes me wonder all the more why they selected the version of the roval they did (much tighter than it needed to be; unnecessarily hard to overtake on; and even requiring, in their eyes, a relocation of the start/restart point).

If they're still satisfied with their choice over the other options, then I'm glad that Vegas is a one-and-done deal; however, it doesn't exactly inspire confidence in them making a good choice for good racing at Indy next season.

Although there is the caveat that it's technically for official FIA championships, Blancpain GT (whatever it's going to be called after this year) is the de facto FIA GT championship. For GTs, and a race duration of 6-12 hours, the minimum circuit length listed on the table in Appendix O is 4.7 km (2.921 miles). Obviously, even the first MotoGP course was shy of that by 0.3 of a mile. Of course, this means Kyalami already has an exception with the IGTC, but 2.85 miles is definitely closer to the desired mark.

I think it's a safe bet that the Turn 5-7 loop will be included to lengthen the lap from 2.439 (2.435) miles, but that takes away quite a bit from the infield stretch. There's really only one way to keep the lap speed up, give the cars a standout section to stretch their legs, and also alleviate the inevitable traffic issues that will come up in an 8-hour race. And I'm not sure that the final corner of the IndyCar or SCCA Runoffs course is going to quite be flat-out in the GT3s. Also, the difference between 2.592 (2.588) miles and 2.534 (2.530) miles is a lot smaller than the difference between either of those and 2.921 miles. (And yes, comparing GA GT in 2013 to IMSA GTD in 2014, the layout using Oval Turn 1 is faster than the IndyCar variant; the cars were uprated and the track was partially repaved for 2014, but average speed was actually a bit slower.)