While pretending I was a race car driver this morning, a question occurred to me:
When you engage the clutch quickly while up-shifting at wide open throttle (i.e. accelerating as fast as possible and WOT only when clutch is engaged, not while actually shifting), there is a large speed difference between the clutch and flywheel over a short period of time, especially on new cars plagued with the dreaded rev hang. Some cars cannot drop the engine speed fast enough to adequately shift quickly (like my 2016 Subaru WRX) and will actually cause a bouncing sensation if you try, which I presume to be the clutch bouncing off the flywheel. My mechanical intuition says this is a bad thing to do. On the other hand, you can practically side-step the clutch on my 1994 Mazda Miata because the RPM drops so quickly.
If you were to shift slowly (but still WOT), the clutch is in contact with the flywheel for a greater period of time, grinding away to pull the needle to the correct RPM for the selected gear. However, this long contact time at different speeds also seems like it would cause a great deal of wear.
Question: What is the optimal clutch engagement speed to mitigate wear at wide open throttle on a car with a manual transmission and petrol engine? Could it actually harm the powertrain in any way on newer cars by shifting too quickly?