Floorless conversion rumors have been around for Mantis for ages, mostly from wishful enthusiasts who want Cedar Point to atone for its 90s Stand-up design to something more comfortable.
However, up until around 2005, riders were allowed to ride Mantis sitting down (that is, lower the restraints to a seated position). Cedar Point eventually did away with this option as it lengthened loading time (not that it already takes the length of an episode of Robot Chicken to load already), but shows that it is possible to ride outside of the "heartline" design and still have it be alright.
Remember, the ride already has a first hill trim and MCBR to control speed, which could be further adjusted for a floorless train.
That is, if any credence is to be given to the 15 year old floorless rumor. :wink: