If there is a problem with clutch slippage, you are much more likely to smell it at very low speeds, not >40MPH.
So maybe test for clutch slippage. Shift from 1st to 3rd instead of 2nd or even 1st to 4th. Try to make the clutch slip. Watch the tach and listen to the motor. Try to detect any slippage such as RPMs slowly dropping after you release the clutch. If the clutch is slipping, it should be obvious. I doubt you'll notice any issues but why not test it and hopefully disprove that seemingly popular theory?
So maybe test for clutch slippage. Shift from 1st to 3rd instead of 2nd or even 1st to 4th. Try to make the clutch slip. Watch the tach and listen to the motor. Try to detect any slippage such as RPMs slowly dropping after you release the clutch. If the clutch is slipping, it should be obvious. I doubt you'll notice any issues but why not test it and hopefully disprove that seemingly popular theory?