To my knowledge, there is a way to game the tube racing system by clipping through walls, waiting for a "reasonable" amount of time, and then clipping back through to have realistic looking yet unbeatable times. I am not accusing anyone - but having messed around with it (deliberately not making any type of time, mind you), it seems viable enough. This change wouldn't affect most races, and even if you made contact once it would not ruin an entire run. However, if you're glitching through, you make contact a lot... I think this is a pretty simple, yet elegant way to fix the problem without overburdening everyone else.

+1 This won't effect anyone who races perfectly. Love this suggestion.

This would only add 1 second for every checkpoint of a race track and still make those times unbeatable by conventional racing.
There is no waiting involved when racing like this. You still have to cover the distance between the start, all checkpoints and the exit as fast as you can.

Here are two runs as an example of how racing and clipping through the walls works (and sometimes doesn't): https://www.youtube.com/watch?v=gawa57qgjdo

if u go fast enough u only suffer 1 hit on the wall, allowing each tap on the wall to only be 0.5 is too low. u can finish em in like 5 wall taps.