Re: Mortise and tenon floor system sagging!
Another problem with hydraulic jacks is that they sometimes creep on you under load. Jack posts are fairly inexpensive and easy to use. If you use a screw or hydraulic jack it is important to build a solid level platform to set the jack on and don't use posts on top of the jack. If you get the beam jacked up and the jack kicks out besides personal injury the sudden dropping of the beam may cause it to crack. Once the beam is in place you can install proper support posts or build a support wall under the beam. I personally don't like using jack posts as a permanent solution.
Be sure you live your life, because you are a long time dead.-Scottish Proverb