We have a new Compaq for DS 17 (nearly 18) months, still RF. We found it quite stiff to tighten the harness each time as well but seems to be a little better now. Luckily it's installed in DH's car and he's stronger than I am, so it gets tightened sufficiently. He would also put one hand on the tightening strap at the feet and pull, and the other hand behind the seat pulling the harness straps firm from behind to help. Is your seat very new still? Maybe it will be a bit looser with time?
Edited by Jamelex, 02 March 2013 - 10:08 AM.