I believe Hi-Lo recommended that the top should stay in the full up position, not on the safety bar. Also, if the top is fully up the gasket around the top and bottom should be fully sealed.

You just contradicted yourself. The weight IS always on the cables when it’s up..never on the safty bar. The safty bar ONLY holds the ram in the extended position (the cables are still doing all the lifting)

As RichR states, Hi Lo recommend full up with the top. However, most hyd cylinders have some internal leakage and may creep down over time, thus the safety bar. That's why when lowering the top, Hi Lo states that the top be raised to the full up, then pull the safety lanyard then lower. As gary54 said, that little bit DOES take some stress off the cables. Just a little bit, but some. The importance of the safety bar prevents injury should a catastrophic failure of the hyd system occur.

Well...I’m not Hi-lo expert but I do understand physics.. and I guarantee you...without a doubt-The safety bar does NOT take ANY stress off of the cables (none-zero). But feel free to operate your trailer however you wish.