They spread slightly over time so they don't need to be tight. The cow mats differ from the horse version (horse version is thicker), but cow stalls also differ so cow mats are usually bolted down at one end.
Mayo mats are much easier to cut (with a Stanley knife) than any of the rubber mats we used previously so fitting them to the stable is straightforward. I fitted them in our previous stables because the floors were cobbled, irregular and drained the wrong way. I used to lift a couple every week and lean them against the wall while I put a hose in to wash underneath - try that with rubber mats.
After a year we moved them to the newly-built stables at home. Since you can pick up a 6*4 mat single handed and they stand up by themselves we just lined them up inside the Ivor Williams. Despite the poor surface they'd been on they remained flat so we installed them in the new stables without problem.
Although the new stables drain properly I still like to lift the mats from time to time and jet wash underneath. Its still a one person job, so it happens more often. But its also easy to lift a corner and shove a hose in.
Last week we took a new and unused rubber mat over to a friend's stables. To move it we had to roll it and tie it up, then it took two of us to lift it into the car. Just a different world, but this is all getting away from the main point - we don't use much bedding and mucking-out is easy and quick, every day.