Yep - the frames are not designed to support the weight of the trailer at the ends or corners, but in the middle, at the axles. IMHO, if you only had 4 supports (jacks), it would be better to put them just in front and just behind the wheels on each side, and leave the corners unsupported - that way you are supporting the unit the same way as going down the road. But if you had the additional 4 jacks under the corners, it would stabilize better.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.