I've made some assumptions, which on reflection could be incorrect. My Tacx Flux does a spindown test where you spin it up to a high RPM, then stop pedalling a

I've made some assumptions, which on reflection could be incorrect. My Tacx Flux does a spindown test where you spin it up to a high RPM, then stop pedalling and it measures how long it takes to stop. I guess it's actually trying to get an accurate measure of the resistance being applied. A heavier flywheel will be harder to spin up, but will also take longer to spin down at the same resistance, so maybe that doesn't make a difference. Pressing something against the flywheel would make the trainer think it's applying more resistance than it really is, so I'm pretty sure that would work.