Thanks for the input (qualified or guts feeling/opinion).
Some thoughts:
Flex: if the frame flexes so much, every time I push it up with the front jack, it will flex (actually same or worse than putting one jack for example at 3/4 point in the rear)
Flex: dynamic flex (bouncing up/down during thousands of miles) would completley desintegrade the house if static lift is flexing so much that i might cause damage.
Force: only a max of 50% of the trailer weight can theoretically be lifted by one jack; it is NOT possible to lift more weight; the other half (likely a lot more) is still resting on the wheels or front jack). The 50% would mean one jack (think: middle of bumper) and front jack, all wheels off the ground. Then 3500 would be on the single rear jack, and 3500 on the front jack.
Using Tires (here: axles): I will do a trial run (already have a hydraulic jack on hand) and lifting one axle at a time to put boards under the tires (or put a jack stand under the axle) to level. Reason for investigating the frame lift option: axles not easily accessible for jacking up.
Using FRAME near AXLE: best of both worlds? Same stress to chassis, yet better accessible than axle. Will try this FIRST (tailer in driveway, tilting terrible to one side).
HAVE to get one (two) of those 'curved' and 'scaled' levels (thanks for the link!).
