I carry a selection of 1" and 2" treated boards with a 45 deg angle cut on one end. I have a 5th wheel and when the trailer is in it's spot I check the large bubble level on the tongue. A short mark is 1" board and a long mark is a 2" board. Pull slightly forward (or backwards) and place the blocks and pull the trailer on them. Put the X-Chocks between the wheels (both sides) and a plastic chock behind (or in front) of the tires not on the boards. drop the landing gear and check the front to back. If more than 1/2 a bubble off either way (especially high in the front) I know there won't be enough travel in the gear to drop the front down to level so I raise the pin point on the landing gear 1 hole above that normal "lock-in" spot to allow more downward movement of the front of the trailer. If the other way I have some 4"x6" blocks. I use those on the back also so the rear doesn't have to go down as far. The further it goes down the closer the pads are to each other and the more unstable. No I haven't invested in JT Strongarms yet.
It takes longer to describe it than to do it.