I love the idea, but 5% is too low IMO. I think I would want 10% minimum before I'd vote for it, and I'd really prefer 15%.

Also, I think things should be taken a step further, regardless of the %. Since most people are doing this to fund other purchases in game anyways (and that's really the only type of cash out we care to aid in anyways), 100% of the SPS should be burned and converted to X% DEC. So we force the use of the flywheel on top of the penalty.