OK, so I ran two of the problem cars around the 'ring tonight. First off the stock NA MX-5, have to be utterly honest it wasn't a problem at all, then I took the R35 out for a trip and I think I may know what some of the issues are that people are finding, particularly at the 'ring. Fuchsrohe is the best example to illustrate this, and I double-checked with a 'ring guide I've got, the compression is absolutely massive at that point, and a 1,700-kilo car arriving at full chat into a compression that deep is going to fully compress the suspension. In a compression that 'ring guides warn you to not brake in, or do anything to unsettle the car, that's only going to be bad news. I found that scrubbing a bit of speed off as you approach the compression is enough to get you through with the car settled.
Now never having driven an R35 through that section I can't attest to how accurate the approach is, but the logic behind the problem and solution are sound enough.
The sense of speed in GT7 (and for most GT titles0 kind of sucks, so it's far too easy to be going a lot quicker than you think.